Three-dimensional data encoding method, three-dimensional data decoding method, three-dimensional data encoding device, and three-dimensional data decoding device

ABSTRACT

A three-dimensional data encoding method includes encoding information of a current node included in an N-ary tree structure of three-dimensional points included in three-dimensional data, where N is an integer greater than or equal to 2. In the encoding, first information is encoded, the first information indicating a range for one or more referable neighboring nodes among neighboring nodes spatially neighboring the current node, and the current node is encoded with reference to a neighboring node within the range.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. continuation application of PCT InternationalPatent Application Number PCT/JP2019/015122 filed on Apr. 5, 2019,claiming the benefit of priority of U.S. Provisional Application No.62/655,525 filed on Apr. 10, 2018, the entire contents of which arehereby incorporated by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to a three-dimensional data encodingmethod, a three-dimensional data decoding method, a three-dimensionaldata encoding device, and a three-dimensional data decoding device.

2. Description of the Related Art

Devices or services utilizing three-dimensional data are expected tofind their widespread use in a wide range of fields, such as computervision that enables autonomous operations of cars or robots, mapinformation, monitoring, infrastructure inspection, and videodistribution. Three-dimensional data is obtained through various meansincluding a distance sensor such as a rangefinder, as well as a stereocamera and a combination of a plurality of monocular cameras.

Methods of representing three-dimensional data include a method known asa point cloud scheme that represents the shape of a three-dimensionalstructure by a point group in a three-dimensional space. In the pointcloud scheme, the positions and colors of a point group are stored.While point cloud is expected to be a mainstream method of representingthree-dimensional data, a massive amount of data of a point groupnecessitates compression of the amount of three-dimensional data byencoding for accumulation and transmission, as in the case of atwo-dimensional moving picture (examples include MPEG-4 AVC and HEVCstandardized by MPEG).

Meanwhile, point cloud compression is partially supported by, forexample, an open-source library (Point Cloud Library) for pointcloud-related processing.

Furthermore, a technique for searching for and displaying a facilitylocated in the surroundings of the vehicle is known (for example, seeInternational Publication WO 2014/020663).

SUMMARY

There has been a demand for reducing an amount of processing in encodingof three-dimensional data.

The present disclosure has an object to provide a three-dimensional dataencoding method, a three-dimensional data decoding method, athree-dimensional data encoding device, or a three-dimensional datadecoding device that is capable of reducing the amount of processing.

A three-dimensional data encoding method according to one aspect of thepresent disclosure includes encoding information of a current nodeincluded in an N-ary tree structure of three-dimensional points includedin three-dimensional data, where N is an integer greater than or equalto 2. In the encoding, first information is encoded, the firstinformation indicating a range for one or more referable neighboringnodes among neighboring nodes spatially neighboring the current node,and the current node is encoded with reference to a neighboring nodewithin the range.

A three-dimensional data decoding method according to one aspect of thepresent disclosure includes decoding information of a current nodeincluded in an N-ary tree structure of three-dimensional points includedin three-dimensional data, where N is an integer greater than or equalto 2. In the decoding, first information is decoded from a bitstream,the first information indicating a range for one or more referableneighboring nodes among neighboring nodes spatially neighboring thecurrent node, and the current node is decoded with reference to aneighboring node within the range.

The present disclosure provides a three-dimensional data encodingmethod, a three-dimensional data decoding method, a three-dimensionaldata encoding device, or a three-dimensional data decoding device thatis capable of reducing an amount of processing.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, advantages and features of the disclosure willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the present disclosure.

FIG. 1 is a diagram showing the structure of encoded three-dimensionaldata according to Embodiment 1;

FIG. 2 is a diagram showing an example of prediction structures amongSPCs that belong to the lowermost layer in a GOS according to Embodiment1;

FIG. 3 is a diagram showing an example of prediction structures amonglayers according to Embodiment 1;

FIG. 4 is a diagram showing an example order of encoding GOSs accordingto Embodiment 1;

FIG. 5 is a diagram showing an example order of encoding GOSs accordingto Embodiment 1;

FIG. 6 is a block diagram of a three-dimensional data encoding deviceaccording to Embodiment 1;

FIG. 7 is a flowchart of encoding processes according to Embodiment 1;

FIG. 8 is a block diagram of a three-dimensional data decoding deviceaccording to Embodiment 1;

FIG. 9 is a flowchart of decoding processes according to Embodiment 1;

FIG. 10 is a diagram showing an example of meta information according toEmbodiment 1;

FIG. 11 is a diagram showing an example structure of a SWLD according toEmbodiment 2;

FIG. 12 is a diagram showing example operations performed by a serverand a client according to Embodiment 2;

FIG. 13 is a diagram showing example operations performed by the serverand a client according to Embodiment 2;

FIG. 14 is a diagram showing example operations performed by the serverand the clients according to Embodiment 2;

FIG. 15 is a diagram showing example operations performed by the serverand the clients according to Embodiment 2;

FIG. 16 is a block diagram of a three-dimensional data encoding deviceaccording to Embodiment 2;

FIG. 17 is a flowchart of encoding processes according to Embodiment 2;

FIG. 18 is a block diagram of a three-dimensional data decoding deviceaccording to Embodiment 2;

FIG. 19 is a flowchart of decoding processes according to Embodiment 2;

FIG. 20 is a diagram showing an example structure of a WLD according toEmbodiment 2;

FIG. 21 is a diagram showing an example octree structure of the WLDaccording to Embodiment 2;

FIG. 22 is a diagram showing an example structure of a SWLD according toEmbodiment 2;

FIG. 23 is a diagram showing an example octree structure of the SWLDaccording to Embodiment 2;

FIG. 24 is a block diagram of a three-dimensional data creation deviceaccording to Embodiment 3;

FIG. 25 is a block diagram of a three-dimensional data transmissiondevice according to Embodiment 3;

FIG. 26 is a block diagram of a three-dimensional information processingdevice according to Embodiment 4;

FIG. 27 is a block diagram of a three-dimensional data creation deviceaccording to Embodiment 5;

FIG. 28 is a diagram showing a structure of a system according toEmbodiment 6;

FIG. 29 is a block diagram of a client device according to Embodiment 6;

FIG. 30 is a block diagram of a server according to Embodiment 6;

FIG. 31 is a flowchart of a three-dimensional data creation processperformed by the client device according to Embodiment 6;

FIG. 32 is a flowchart of a sensor information transmission processperformed by the client device according to Embodiment 6;

FIG. 33 is a flowchart of a three-dimensional data creation processperformed by the server according to Embodiment 6;

FIG. 34 is a flowchart of a three-dimensional map transmission processperformed by the server according to Embodiment 6;

FIG. 35 is a diagram showing a structure of a variation of the systemaccording to Embodiment 6;

FIG. 36 is a diagram showing a structure of the server and clientdevices according to Embodiment 6;

FIG. 37 is a block diagram of a three-dimensional data encoding deviceaccording to Embodiment 7;

FIG. 38 is a diagram showing an example of a prediction residualaccording to Embodiment 7;

FIG. 39 is a diagram showing an example of a volume according toEmbodiment 7;

FIG. 40 is a diagram showing an example of an octree representation ofthe volume according to Embodiment 7;

FIG. 41 is a diagram showing an example of bit sequences of the volumeaccording to Embodiment 7;

FIG. 42 is a diagram showing an example of an octree representation of avolume according to Embodiment 7;

FIG. 43 is a diagram showing an example of the volume according toEmbodiment 7;

FIG. 44 is a diagram for describing an intra prediction processaccording to Embodiment 7;

FIG. 45 is a diagram for describing a rotation and translation processaccording to Embodiment 7;

FIG. 46 is a diagram showing an example syntax of an RT flag and RTinformation according to Embodiment 7;

FIG. 47 is a diagram for describing an inter prediction processaccording to Embodiment 7;

FIG. 48 is a block diagram of a three-dimensional data decoding deviceaccording to Embodiment 7;

FIG. 49 is a flowchart of a three-dimensional data encoding processperformed by the three-dimensional data encoding device according toEmbodiment 7;

FIG. 50 is a flowchart of a three-dimensional data decoding processperformed by the three-dimensional data decoding device according toEmbodiment 7;

FIG. 51 is a diagram showing a structure of a distribution systemaccording to Embodiment 8;

FIG. 52 is a diagram showing an example structure of a bitstream of anencoded three-dimensional map according to Embodiment 8;

FIG. 53 is a diagram for describing an advantageous effect on encodingefficiency according to Embodiment 8;

FIG. 54 is a flowchart of processes performed by a server according toEmbodiment 8;

FIG. 55 is a flowchart of processes performed by a client according toEmbodiment 8;

FIG. 56 is a diagram showing an example syntax of a submap according toEmbodiment 8;

FIG. 57 is a diagram schematically showing a switching process of anencoding type according to Embodiment 8;

FIG. 58 is a diagram showing an example syntax of a submap according toEmbodiment 8;

FIG. 59 is a flowchart of a three-dimensional data encoding processaccording to Embodiment 8;

FIG. 60 is a flowchart of a three-dimensional data decoding processaccording to Embodiment 8;

FIG. 61 is a diagram schematically showing an operation of a variationof the switching process of the encoding type according to Embodiment 8;

FIG. 62 is a diagram schematically showing an operation of a variationof the switching process of the encoding type according to Embodiment 8;

FIG. 63 is a diagram schematically showing an operation of a variationof the switching process of the encoding type according to Embodiment 8;

FIG. 64 is a diagram schematically showing an operation of a variationof a calculation process of a differential value according to Embodiment8;

FIG. 65 is a diagram schematically showing an operation of a variationof the calculation process of the differential value according toEmbodiment 8;

FIG. 66 is a diagram schematically showing an operation of a variationof the calculation process of the differential value according toEmbodiment 8;

FIG. 67 is a diagram schematically showing an operation of a variationof the calculation process of the differential value according toEmbodiment 8;

FIG. 68 is a diagram showing an example syntax of a volume according toEmbodiment 8;

FIG. 69 is a diagram showing an example of an important area accordingto Embodiment 9;

FIG. 70 is a diagram showing an example of an occupancy code accordingto Embodiment 9;

FIG. 71 is a diagram showing an example of a quadtree structureaccording to Embodiment 9;

FIG. 72 is a diagram showing an example of an occupancy code and alocation code according to Embodiment 9;

FIG. 73 is a diagram showing an example of three-dimensional pointsobtained through LiDAR according to Embodiment 9;

FIG. 74 is a diagram showing an example of an octree structure accordingto Embodiment 9;

FIG. 75 is a diagram showing an example of hybrid encoding according toEmbodiment 9;

FIG. 76 is a diagram for describing a method for switching betweenlocation encoding and occupancy encoding according to Embodiment 9;

FIG. 77 is a diagram showing an example of a location encoded bitstreamaccording to Embodiment 9;

FIG. 78 is a diagram showing an example of a hybrid encoded bitstreamaccording to Embodiment 9;

FIG. 79 is a diagram showing an occupancy code tree structure ofimportant three-dimensional points according to Embodiment 9;

FIG. 80 is a diagram showing an occupancy code tree structure ofnon-important three-dimensional points according to Embodiment 9;

FIG. 81 is a diagram showing an example of a hybrid encoded bitstreamaccording to Embodiment 9;

FIG. 82 is a diagram showing an example of a bitstream includingencoding mode information according to Embodiment 9;

FIG. 83 is a diagram showing an example syntax according to Embodiment9;

FIG. 84 is a flowchart of an encoding process according to Embodiment 9;

FIG. 85 is a flowchart of a node encoding process according toEmbodiment 9;

FIG. 86 is a flowchart of a decoding process according to Embodiment 9;

FIG. 87 is a flowchart of a node decoding process according toEmbodiment 9;

FIG. 88 is a diagram illustrating an example of a tree structureaccording to Embodiment 10;

FIG. 89 is a graph showing an example of the number of valid leaves ofeach branch according to Embodiment 10;

FIG. 90 is a diagram illustrating an application example of encodingschemes according to Embodiment 10;

FIG. 91 is a diagram illustrating an example of a dense branch areaaccording to Embodiment 10;

FIG. 92 is a diagram illustrating an example of a densethree-dimensional point cloud according to Embodiment 10;

FIG. 93 is a diagram illustrating an example of a sparsethree-dimensional point cloud according to Embodiment 10;

FIG. 94 is a flowchart of an encoding process according to Embodiment10;

FIG. 95 is a flowchart of a decoding process according to Embodiment 10;

FIG. 96 is a flowchart of an encoding process according to Embodiment10;

FIG. 97 is a flowchart of a decoding process according to Embodiment 10;

FIG. 98 is a flowchart of an encoding process according to Embodiment10;

FIG. 99 is a flowchart of a decoding process according to Embodiment 10;

FIG. 100 is a flowchart of a process of separating three-dimensionalpoints according to Embodiment 10;

FIG. 101 is a diagram illustrating an example of a syntax according toEmbodiment 10;

FIG. 102 is a diagram illustrating an example of a dense branchaccording to Embodiment 10;

FIG. 103 is a diagram illustrating an example of a sparse branchaccording to Embodiment 10;

FIG. 104 is a flowchart of an encoding process according to a variationof Embodiment 10;

FIG. 105 is a flowchart of a decoding process according to the variationof Embodiment 10;

FIG. 106 is a flowchart of a process of separating three-dimensionalpoints according to the variation of Embodiment 10;

FIG. 107 is a diagram illustrating an example of a syntax according tothe variation of Embodiment 10;

FIG. 108 is a flowchart of an encoding process according to Embodiment10;

FIG. 109 is a flowchart of a decoding process according to Embodiment10;

FIG. 110 is a diagram illustrating an example of a tree structureaccording to Embodiment 11;

FIG. 111 is a diagram illustrating an example of occupancy codesaccording to Embodiment 11;

FIG. 112 is a diagram schematically illustrating an operation performedby a three-dimensional data encoding device according to Embodiment 11;

FIG. 113 is a diagram illustrating an example of geometry informationaccording to Embodiment 11;

FIG. 114 is a diagram illustrating an example of selecting a codingtable using geometry information according to Embodiment 11;

FIG. 115 is a diagram illustrating an example of selecting a codingtable using structure information according to Embodiment 11;

FIG. 116 is a diagram illustrating an example of selecting a codingtable using attribute information according to Embodiment 11;

FIG. 117 is a diagram illustrating an example of selecting a codingtable using attribute information according to Embodiment 11;

FIG. 118 is a diagram illustrating an example of a structure of abitstream according to Embodiment 11;

FIG. 119 is a diagram illustrating an example of a coding tableaccording to Embodiment 11;

FIG. 120 is a diagram illustrating an example of a coding tableaccording to Embodiment 11;

FIG. 121 is a diagram illustrating an example of a structure of abitstream according to Embodiment 11;

FIG. 122 is a diagram illustrating an example of a coding tableaccording to Embodiment 11;

FIG. 123 is a diagram illustrating an example of a coding tableaccording to Embodiment 11;

FIG. 124 is a diagram illustrating an example of bit numbers of anoccupancy code according to Embodiment 11;

FIG. 125 is a flowchart of an encoding process using geometryinformation according to Embodiment 11;

FIG. 126 is a flowchart of a decoding process using geometry informationaccording to Embodiment 11;

FIG. 127 is a flowchart of an encoding process using structureinformation according to Embodiment 11;

FIG. 128 is a flowchart of a decoding process using structureinformation according to Embodiment 11;

FIG. 129 is a flowchart of an encoding process using attributeinformation according to Embodiment 11;

FIG. 130 is a flowchart of a decoding process using attributeinformation according to Embodiment 11;

FIG. 131 is a flowchart of a process of selecting a coding table usinggeometry information according to Embodiment 11;

FIG. 132 is a flowchart of a process of selecting a coding table usingstructure information according to Embodiment 11;

FIG. 133 is a flowchart of a process of selecting a coding table usingattribute information according to Embodiment 11;

FIG. 134 is a block diagram of a three-dimensional data encoding deviceaccording to Embodiment 11;

FIG. 135 is a block diagram of a three-dimensional data decoding deviceaccording to Embodiment 11;

FIG. 136 is a diagram illustrating a reference relationship in an octreestructure according to Embodiment 12;

FIG. 137 is a diagram illustrating a reference relationship in a spatialregion according to Embodiment 12;

FIG. 138 is a diagram illustrating an example of neighboring referencenodes according to Embodiment 12;

FIG. 139 is a diagram illustrating a relationship between a parent nodeand nodes according to Embodiment 12;

FIG. 140 is a diagram illustrating an example of an occupancy code ofthe parent node according to Embodiment 12;

FIG. 141 is a block diagram of a three-dimensional data encoding deviceaccording to Embodiment 12;

FIG. 142 is a block diagram of a three-dimensional data decoding deviceaccording to Embodiment 12;

FIG. 143 is a flowchart of a three-dimensional data encoding processaccording to Embodiment 12;

FIG. 144 is a flowchart of a three-dimensional data decoding processaccording to Embodiment 12;

FIG. 145 is a diagram illustrating an example of selecting a codingtable according to Embodiment 12;

FIG. 146 is a diagram illustrating a reference relationship in a spatialregion according to Variation 1 of Embodiment 12;

FIG. 147 is a diagram illustrating an example of a syntax of headerinformation according to Variation 1 of Embodiment 12;

FIG. 148 is a diagram illustrating an example of a syntax of headerinformation according to Variation 1 of Embodiment 12;

FIG. 149 is a diagram illustrating an example of neighboring referencenodes according to Variation 2 of Embodiment 12;

FIG. 150 is a diagram illustrating an example of a current node andneighboring nodes according to Variation 2 of Embodiment 12;

FIG. 151 is a diagram illustrating a reference relationship in an octreestructure according to Variation 3 of Embodiment 12;

FIG. 152 is a diagram illustrating a reference relationship in a spatialregion according to Variation 3 of Embodiment 12;

FIG. 153 is a diagram illustrating an example of a syntax of headerinformation according to Embodiment 13;

FIG. 154 is a diagram illustrating a configuration example of an octreewhen mode information according to Embodiment 13 indicates 1;

FIG. 155 is a diagram illustrating a configuration example of an octreewhen mode information according to Embodiment 13 indicates 0;

FIG. 156 is a diagram illustrating an example of a syntax of informationof a node according to Embodiment 13;

FIG. 157 is a flowchart of a three-dimensional data encoding processaccording to Embodiment 13;

FIG. 158 is a flowchart of a three-dimensional data decoding processaccording to Embodiment 13;

FIG. 159 is a block diagram of a three-dimensional data encoding deviceaccording to Embodiment 13;

FIG. 160 is a block diagram of a three-dimensional data decoding deviceaccording to Embodiment 13;

FIG. 161 is a flowchart of a three-dimensional data encoding processaccording to Embodiment 13;

FIG. 162 is a flowchart of a three-dimensional data decoding processaccording to Embodiment 13;

FIG. 163 is a diagram illustrating examples of a 1-bit occupied positionand a remaining bit according to Embodiment 14;

FIG. 164 is a diagram for illustrating a process of determining whetherto apply occupied position encoding according to Embodiment 14;

FIG. 165 is a diagram illustrating an example of a syntax of informationof a node according to Embodiment 14;

FIG. 166 is a flowchart of a three-dimensional data encoding processaccording to Embodiment 14;

FIG. 167 is a flowchart of an occupied position encoding processaccording to Embodiment 14;

FIG. 168 is a flowchart of a three-dimensional data decoding processaccording to Embodiment 14;

FIG. 169 is a flowchart of an occupied position decoding processaccording to Embodiment 14;

FIG. 170 is a block diagram of a three-dimensional data encoding deviceaccording to Embodiment 14;

FIG. 171 is a block diagram of a three-dimensional data decoding deviceaccording to Embodiment 14;

FIG. 172 is a flowchart of a three-dimensional data encoding processaccording to Embodiment 14;

FIG. 173 is a flowchart of a three-dimensional data decoding processaccording to Embodiment 14;

FIG. 174 is a diagram for illustrating duplicated points according toEmbodiment 15;

FIG. 175 is a diagram for illustrating a process performed on duplicatedpoints according to Embodiment 15;

FIG. 176 is a diagram illustrating an example of a syntax of headerinformation according to Embodiment 15;

FIG. 177 is a diagram illustrating an example of a syntax of informationof a node according to Embodiment 15;

FIG. 178 is a flowchart of a three-dimensional data encoding processaccording to Embodiment 15;

FIG. 179 is a flowchart of the three-dimensional data encoding processaccording to Embodiment 15;

FIG. 180 is a flowchart of a three-dimensional data decoding processaccording to Embodiment 15;

FIG. 181 is a block diagram of a three-dimensional data decoding deviceaccording to Embodiment 15;

FIG. 182 is a block diagram of a three-dimensional data decoding deviceaccording to Embodiment 15;

FIG. 183 is a flowchart of a variation of the three-dimensional dataencoding process according to Embodiment 15;

FIG. 184 is a diagram for illustrating a process for duplicated pointsaccording to Embodiment 15;

FIG. 185 is a diagram illustrating an example of neighboring nodesaccording to Embodiment 16;

FIG. 186 is a diagram illustrating an example of nodes to be searchedaccording to Embodiment 16;

FIG. 187 is a diagram for illustrating a search process for aneighboring node according to Embodiment 16;

FIG. 188 is a diagram for illustrating an update process for neighboringinformation according to Embodiment 16;

FIG. 189 is a diagram for illustrating an update process for neighboringinformation according to Embodiment 16;

FIG. 190 is a diagram for illustrating a search process for which asearch threshold value is provided according to Embodiment 16;

FIG. 191 is a diagram illustrating an example of indexes for whichMorton codes are used according to Embodiment 16;

FIG. 192 is a diagram illustrating an example of a queue for whichMorton codes are used according to Embodiment 16;

FIG. 193 is a block diagram of a three-dimensional data encoding deviceaccording to Embodiment 16;

FIG. 194 is a block diagram of a three-dimensional data decoding deviceaccording to Embodiment 16;

FIG. 195 is a flowchart of a three-dimensional data encoding processaccording to Embodiment 16;

FIG. 196 is a flowchart of a three-dimensional data decoding processaccording to Embodiment 16;

FIG. 197 is a diagram illustrating an example of a syntax of headerinformation according to Embodiment 16;

FIG. 198 is a diagram illustrating an example of a syntax of informationof a node according to Embodiment 16;

FIG. 199 is a flowchart of a three-dimensional data encoding processaccording to Embodiment 16;

FIG. 200 is a flowchart of a three-dimensional data decoding processaccording to Embodiment 16;

FIG. 201 is a flowchart of a three-dimensional data encoding processaccording to Embodiment 16; and

FIG. 202 is a flowchart of a three-dimensional data decoding processaccording to Embodiment 16.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A three-dimensional data encoding method according to one aspect of thepresent disclosure includes encoding information of a current nodeincluded in an N-ary tree structure of three-dimensional points includedin three-dimensional data, where N is an integer greater than or equalto 2. In the encoding, first information is encoded, the firstinformation indicating a range for one or more referable neighboringnodes among neighboring nodes spatially neighboring the current node,and the current node is encoded with reference to a neighboring nodewithin the range.

With this, since the three-dimensional data encoding method makes itpossible to limit referable neighboring nodes, the three-dimensionaldata encoding method makes it possible to reduce the amount ofprocessing.

For example, in the encoding, a coding table may be selected based onwhether the neighboring node within the range includes athree-dimensional point, and the information of the current node may beentropy encoded using the coding table selected.

For example, in the encoding, a search may be performed for informationof the one or more referable neighboring nodes among the neighboringnodes spatially neighboring the current node, and the first informationmay indicate a range for the search.

For example, in the search, information of nodes may be searched for ina predetermined order, and the first information may indicate a totalnumber of nodes on which the search is to be performed.

For example, in the search, indexes of Morton codes may be used.

For example, in the encoding, second information may be encoded, thesecond information indicating whether the range for the one or morereferable neighboring nodes is to be limited, and the first informationmay be encoded when the second information indicates that the range forthe one or more referable neighboring nodes is to be limited.

For example, the range for the one or more referable neighboring nodesmay change according to a layer to which the current node belongs in theN-ary tree structure.

A three-dimensional data decoding method according to one aspect of thepresent disclosure includes decoding information of a current nodeincluded in an N-ary tree structure of three-dimensional points includedin three-dimensional data, where N is an integer greater than or equalto 2. In the decoding, first information is decoded from a bitstream,the first information indicating a range for one or more referableneighboring nodes among neighboring nodes spatially neighboring thecurrent node, and the current node is decoded with reference to aneighboring node within the range.

With this, since the three-dimensional data decoding method makes itpossible to limit referable neighboring nodes, the three-dimensionaldata decoding method makes it possible to reduce the amount ofprocessing.

For example, in the decoding, a coding table may be selected based onwhether the neighboring node within the range includes athree-dimensional point, and the information of the current node may beentropy decoded using the coding table selected.

For example, in the decoding, a search may be performed for informationof the one or more referable neighboring nodes among the neighboringnodes spatially neighboring the current node, and the first informationmay indicate a range for the search.

For example, in the search, information of nodes may be searched for ina predetermined order, and the first information may indicate a totalnumber of nodes on which the search is to be performed.

For example, in the search, indexes of Morton codes may be used.

For example, in the decoding, second information may be decoded, thesecond information indicating whether the range for the one or morereferable neighboring nodes is to be limited, and the first informationmay be decoded when the second information indicates that the range forthe one or more referable neighboring nodes is to be limited.

For example, the range for the one or more referable neighboring nodesmay change according to a layer to which the current node belongs in theN-ary tree structure.

A three-dimensional data encoding device according to one aspect of thepresent disclosure includes a processor and memory. Using the memory,the processor encodes information of a current node included in an N-arytree structure of three-dimensional points included in three-dimensionaldata, where N is an integer greater than or equal to 2. In the encoding,first information is encoded, the first information indicating a rangefor one or more referable neighboring nodes among neighboring nodesspatially neighboring the current node, and the current node is encodedwith reference to a neighboring node within the range.

With this, since the three-dimensional data encoding device limitsreferable neighboring nodes, the three-dimensional data encoding devicereduces the amount of processing.

A three-dimensional data decoding device according to one aspect of thepresent disclosure includes a processor and memory. Using the memory,the processor decodes information of a current node included in an N-arytree structure of three-dimensional points included in three-dimensionaldata, where N is an integer greater than or equal to 2. In the decoding,first information is decoded from a bitstream, the first informationindicating a range for one or more referable neighboring nodes amongneighboring nodes spatially neighboring the current node, and thecurrent node is decoded with reference to a neighboring node within therange.

With this, since the three-dimensional data decoding device limitsreferable neighboring nodes, the three-dimensional data decoding devicereduces the amount of processing.

Note that these general or specific aspects may be implemented as asystem, a method, an integrated circuit, a computer program, or acomputer-readable recording medium such as a CD-ROM, or may beimplemented as any combination of a system, a method, an integratedcircuit, a computer program, and a recording medium.

The following describes embodiments with reference to the drawings. Notethat the following embodiments show exemplary embodiments of the presentdisclosure. The numerical values, shapes, materials, structuralcomponents, the arrangement and connection of the structural components,steps, the processing order of the steps, etc. shown in the followingembodiments are mere examples, and thus are not intended to limit thepresent disclosure. Of the structural components described in thefollowing embodiments, structural components not recited in any one ofthe independent claims that indicate the broadest concepts will bedescribed as optional structural components.

Embodiment 1

First, the data structure of encoded three-dimensional data (hereinafteralso referred to as encoded data) according to the present embodimentwill be described. FIG. 1 is a diagram showing the structure of encodedthree-dimensional data according to the present embodiment.

In the present embodiment, a three-dimensional space is divided intospaces (SPCs), which correspond to pictures in moving picture encoding,and the three-dimensional data is encoded on a SPC-by-SPC basis. EachSPC is further divided into volumes (VLMs), which correspond tomacroblocks, etc. in moving picture encoding, and predictions andtransforms are performed on a VLM-by-VLM basis. Each volume includes aplurality of voxels (VXLs), each being a minimum unit in which positioncoordinates are associated. Note that prediction is a process ofgenerating predictive three-dimensional data analogous to a currentprocessing unit by referring to another processing unit, and encoding adifferential between the predictive three-dimensional data and thecurrent processing unit, as in the case of predictions performed ontwo-dimensional images. Such prediction includes not only spatialprediction in which another prediction unit corresponding to the sametime is referred to, but also temporal prediction in which a predictionunit corresponding to a different time is referred to.

When encoding a three-dimensional space represented by point group datasuch as a point cloud, for example, the three-dimensional data encodingdevice (hereinafter also referred to as the encoding device) encodes thepoints in the point group or points included in the respective voxels ina collective manner, in accordance with a voxel size. Finer voxelsenable a highly-precise representation of the three-dimensional shape ofa point group, while larger voxels enable a rough representation of thethree-dimensional shape of a point group.

Note that the following describes the case where three-dimensional datais a point cloud, but three-dimensional data is not limited to a pointcloud, and thus three-dimensional data of any format may be employed.

Also note that voxels with a hierarchical structure may be used. In sucha case, when the hierarchy includes n levels, whether a sampling pointis included in the n−1th level or its lower levels (the lower levels ofthe n-th level) may be sequentially indicated. For example, when onlythe n-th level is decoded, and the n−1th level or its lower levelsinclude a sampling point, the n-th level can be decoded on theassumption that a sampling point is included at the center of a voxel inthe n-th level.

Also, the encoding device obtains point group data, using, for example,a distance sensor, a stereo camera, a monocular camera, a gyroscopesensor, or an inertial sensor.

As in the case of moving picture encoding, each SPC is classified intoone of at least the three prediction structures that include: intra SPC(I-SPC), which is individually decodable; predictive SPC (P-SPC) capableof only a unidirectional reference; and bidirectional SPC (B-SPC)capable of bidirectional references. Each SPC includes two types of timeinformation: decoding time and display time.

Furthermore, as shown in FIG. 1, a processing unit that includes aplurality of SPCs is a group of spaces (GOS), which is a random accessunit. Also, a processing unit that includes a plurality of GOSs is aworld (WLD).

The spatial region occupied by each world is associated with an absoluteposition on earth, by use of, for example, GPS, or latitude andlongitude information. Such position information is stored asmeta-information. Note that meta-information may be included in encodeddata, or may be transmitted separately from the encoded data.

Also, inside a GOS, all SPCs may be three-dimensionally adjacent to oneanother, or there may be a SPC that is not three-dimensionally adjacentto another SPC.

Note that the following also describes processes such as encoding,decoding, and reference to be performed on three-dimensional dataincluded in processing units such as GOS, SPC, and VLM, simply asperforming encoding/to encode, decoding/to decode, referring to, etc. ona processing unit. Also note that three-dimensional data included in aprocessing unit includes, for example, at least one pair of a spatialposition such as three-dimensional coordinates and an attribute valuesuch as color information.

Next, the prediction structures among SPCs in a GOS will be described. Aplurality of SPCs in the same GOS or a plurality of VLMs in the same SPCoccupy mutually different spaces, while having the same time information(the decoding time and the display time).

A SPC in a GOS that comes first in the decoding order is an I-SPC. GOSscome in two types: closed GOS and open GOS. A closed GOS is a GOS inwhich all SPCs in the GOS are decodable when decoding starts from thefirst I-SPC. Meanwhile, an open GOS is a GOS in which a different GOS isreferred to in one or more SPCs preceding the first I-SPC in the GOS inthe display time, and thus cannot be singly decoded.

Note that in the case of encoded data of map information, for example, aWLD is sometimes decoded in the backward direction, which is opposite tothe encoding order, and thus backward reproduction is difficult whenGOSs are interdependent. In such a case, a closed GOS is basically used.

Each GOS has a layer structure in height direction, and SPCs aresequentially encoded or decoded from SPCs in the bottom layer;

FIG. 2 is a diagram showing an example of prediction structures amongSPCs that belong to the lowermost layer in a GOS. FIG. 3 is a diagramshowing an example of prediction structures among layers.

A GOS includes at least one I-SPC. Of the objects in a three-dimensionalspace, such as a person, an animal, a car, a bicycle, a signal, and abuilding serving as a landmark, a small-sized object is especiallyeffective when encoded as an I-SPC. When decoding a GOS at a lowthroughput or at a high speed, for example, the three-dimensional datadecoding device (hereinafter also referred to as the decoding device)decodes only I-SPC(s) in the GOS.

The encoding device may also change the encoding interval or theappearance frequency of I-SPCs, depending on the degree of sparsenessand denseness of the objects in a WLD.

In the structure shown in FIG. 3, the encoding device or the decodingdevice encodes or decodes a plurality of layers sequentially from thebottom layer (layer 1). This increases the priority of data on theground and its vicinity, which involve a larger amount of information,when, for example, a self-driving car is concerned.

Regarding encoded data used for a drone, for example, encoding ordecoding may be performed sequentially from SPCs in the top layer in aGOS in height direction.

The encoding device or the decoding device may also encode or decode aplurality of layers in a manner that the decoding device can have arough grasp of a GOS first, and then the resolution is graduallyincreased. The encoding device or the decoding device may performencoding or decoding in the order of layers 3, 8, 1, 9 . . . , forexample.

Next, the handling of static objects and dynamic objects will bedescribed.

A three-dimensional space includes scenes or still objects such as abuilding and a road (hereinafter collectively referred to as staticobjects), and objects with motion such as a car and a person(hereinafter collectively referred to as dynamic objects). Objectdetection is separately performed by, for example, extracting keypointsfrom point cloud data, or from video of a camera such as a stereocamera. In this description, an example method of encoding a dynamicobject will be described.

A first method is a method in which a static object and a dynamic objectare encoded without distinction. A second method is a method in which adistinction is made between a static object and a dynamic object on thebasis of identification information.

For example, a GOS is used as an identification unit. In such a case, adistinction is made between a GOS that includes SPCs constituting astatic object and a GOS that includes SPCs constituting a dynamicobject, on the basis of identification information stored in the encodeddata or stored separately from the encoded data.

Alternatively, a SPC may be used as an identification unit. In such acase, a distinction is made between a SPC that includes VLMsconstituting a static object and a SPC that includes VLMs constituting adynamic object, on the basis of the identification information thusdescribed.

Alternatively, a VLM or a VXL may be used as an identification unit. Insuch a case, a distinction is made between a VLM or a VXL that includesa static object and a VLM or a VXL that includes a dynamic object, onthe basis of the identification information thus described.

The encoding device may also encode a dynamic object as at least one VLMor SPC, and may encode a VLM or a SPC including a static object and aSPC including a dynamic object as mutually different GOSs. When the GOSsize is variable depending on the size of a dynamic object, the encodingdevice separately stores the GOS size as meta-information.

The encoding device may also encode a static object and a dynamic objectseparately from each other, and may superimpose the dynamic object ontoa world constituted by static objects. In such a case, the dynamicobject is constituted by at least one SPC, and each SPC is associatedwith at least one SPC constituting the static object onto which the eachSPC is to be superimposed. Note that a dynamic object may be representednot by SPC(s) but by at least one VLM or VXL.

The encoding device may also encode a static object and a dynamic objectas mutually different streams.

The encoding device may also generate a GOS that includes at least oneSPC constituting a dynamic object. The encoding device may further setthe size of a GOS including a dynamic object (GOS_M) and the size of aGOS including a static object corresponding to the spatial region ofGOS_M at the same size (such that the same spatial region is occupied).This enables superimposition to be performed on a GOS-by-GOS basis.

SPC(s) included in another encoded GOS may be referred to in a P-SPC ora B-SPC constituting a dynamic object. In the case where the position ofa dynamic object temporally changes, and the same dynamic object isencoded as an object in a GOS corresponding to a different time,referring to SPC(s) across GOSs is effective in terms of compressionrate.

The first method and the second method may be selected in accordancewith the intended use of encoded data. When encoded three-dimensionaldata is used as a map, for example, a dynamic object is desired to beseparated, and thus the encoding device uses the second method.Meanwhile, the encoding device uses the first method when the separationof a dynamic object is not required such as in the case wherethree-dimensional data of an event such as a concert and a sports eventis encoded.

The decoding time and the display time of a GOS or a SPC are storable inencoded data or as meta-information. All static objects may have thesame time information. In such a case, the decoding device may determinethe actual decoding time and display time. Alternatively, a differentvalue may be assigned to each GOS or SPC as the decoding time, and thesame value may be assigned as the display time. Furthermore, as in thecase of the decoder model in moving picture encoding such asHypothetical Reference Decoder (HRD) compliant with HEVC, a model may beemployed that ensures that a decoder can perform decoding without failby having a buffer of a predetermined size and by reading a bitstream ata predetermined bit rate in accordance with the decoding times.

Next, the topology of GOSs in a world will be described. The coordinatesof the three-dimensional space in a world are represented by the threecoordinate axes (x axis, y axis, and z axis) that are orthogonal to oneanother. A predetermined rule set for the encoding order of GOSs enablesencoding to be performed such that spatially adjacent GOSs arecontiguous in the encoded data. In an example shown in FIG. 4, forexample, GOSs in the x and z planes are successively encoded. After thecompletion of encoding all GOSs in certain x and z planes, the value ofthe y axis is updated. Stated differently, the world expands in the yaxis direction as the encoding progresses. The GOS index numbers are setin accordance with the encoding order.

Here, the three-dimensional spaces in the respective worlds arepreviously associated one-to-one with absolute geographical coordinatessuch as GPS coordinates or latitude/longitude coordinates.Alternatively, each three-dimensional space may be represented as aposition relative to a previously set reference position. The directionsof the x axis, the y axis, and the z axis in the three-dimensional spaceare represented by directional vectors that are determined on the basisof the latitudes and the longitudes, etc. Such directional vectors arestored together with the encoded data as meta-information.

GOSs have a fixed size, and the encoding device stores such size asmeta-information. The GOS size may be changed depending on, for example,whether it is an urban area or not, or whether it is inside or outsideof a room. Stated differently, the GOS size may be changed in accordancewith the amount or the attributes of objects with information values.Alternatively, in the same world, the encoding device may adaptivelychange the GOS size or the interval between I-SPCs in GOSs in accordancewith the object density, etc. For example, the encoding device sets theGOS size to smaller and the interval between I-SPCs in GOSs to shorter,as the object density is higher.

In an example shown in FIG. 5, to enable random access with a finergranularity, a GOS with a high object density is partitioned into theregions of the third to tenth GOSs. Note that the seventh to tenth GOSsare located behind the third to sixth GOSs.

Next, the structure and the operation flow of the three-dimensional dataencoding device according to the present embodiment will be described.FIG. 6 is a block diagram of three-dimensional data encoding device 100according to the present embodiment. FIG. 7 is a flowchart of an exampleoperation performed by three-dimensional data encoding device 100.

Three-dimensional data encoding device 100 shown in FIG. 6 encodesthree-dimensional data 111, thereby generating encoded three-dimensionaldata 112. Such three-dimensional data encoding device 100 includesobtainer 101, encoding region determiner 102, divider 103, and encoder104.

As shown in FIG. 7, first, obtainer 101 obtains three-dimensional data111, which is point group data (S101).

Next, encoding region determiner 102 determines a current region forencoding from among spatial regions corresponding to the obtained pointgroup data (S102). For example, in accordance with the position of auser or a vehicle, encoding region determiner 102 determines, as thecurrent region, a spatial region around such position.

Next, divider 103 divides the point group data included in the currentregion into processing units. The processing units here means units suchas GOSs and SPCs described above. The current region here correspondsto, for example, a world described above. More specifically, divider 103divides the point group data into processing units on the basis of apredetermined GOS size, or the presence/absence/size of a dynamic object(S103). Divider 103 further determines the starting position of the SPCthat comes first in the encoding order in each GOS.

Next, encoder 104 sequentially encodes a plurality of SPCs in each GOS,thereby generating encoded three-dimensional data 112 (S104).

Note that although an example is described here in which the currentregion is divided into GOSs and SPCs, after which each GOS is encoded,the processing steps are not limited to this order. For example, stepsmay be employed in which the structure of a single GOS is determined,which is followed by the encoding of such GOS, and then the structure ofthe subsequent GOS is determined.

As thus described, three-dimensional data encoding device 100 encodesthree-dimensional data 111, thereby generating encoded three-dimensionaldata 112. More specifically, three-dimensional data encoding device 100divides three-dimensional data into first processing units (GOSs), eachbeing a random access unit and being associated with three-dimensionalcoordinates, divides each of the first processing units (GOSs) intosecond processing units (SPCs), and divides each of the secondprocessing units (SPCs) into third processing units (VLMs). Each of thethird processing units (VLMs) includes at least one voxel (VXL), whichis the minimum unit in which position information is associated.

Next, three-dimensional data encoding device 100 encodes each of thefirst processing units (GOSs), thereby generating encodedthree-dimensional data 112. More specifically, three-dimensional dataencoding device 100 encodes each of the second processing units (SPCs)in each of the first processing units (GOSs). Three-dimensional dataencoding device 100 further encodes each of the third processing units(VLMs) in each of the second processing units (SPCs).

When a current first processing unit (GOS) is a closed GOS, for example,three-dimensional data encoding device 100 encodes a current secondprocessing unit (SPC) included in such current first processing unit(GOS) by referring to another second processing unit (SPC) included inthe current first processing unit (GOS). Stated differently,three-dimensional data encoding device 100 refers to no secondprocessing unit (SPC) included in a first processing unit (GOS) that isdifferent from the current first processing unit (GOS).

Meanwhile, when a current first processing unit (GOS) is an open GOS,three-dimensional data encoding device 100 encodes a current secondprocessing unit (SPC) included in such current first processing unit(GOS) by referring to another second processing unit (SPC) included inthe current first processing unit (GOS) or a second processing unit(SPC) included in a first processing unit (GOS) that is different fromthe current first processing unit (GOS).

Also, three-dimensional data encoding device 100 selects, as the type ofa current second processing unit (SPC), one of the following: a firsttype (I-SPC) in which another second processing unit (SPC) is notreferred to; a second type (P-SPC) in which another single secondprocessing unit (SPC) is referred to; and a third type in which othertwo second processing units (SPC) are referred to. Three-dimensionaldata encoding device 100 encodes the current second processing unit(SPC) in accordance with the selected type.

Next, the structure and the operation flow of the three-dimensional datadecoding device according to the present embodiment will be described.FIG. 8 is a block diagram of three-dimensional data decoding device 200according to the present embodiment. FIG. 9 is a flowchart of an exampleoperation performed by three-dimensional data decoding device 200.

Three-dimensional data decoding device 200 shown in FIG. 8 decodesencoded three-dimensional data 211, thereby generating decodedthree-dimensional data 212. Encoded three-dimensional data 211 here is,for example, encoded three-dimensional data 112 generated bythree-dimensional data encoding device 100. Such three-dimensional datadecoding device 200 includes obtainer 201, decoding start GOS determiner202, decoding SPC determiner 203, and decoder 204.

First, obtainer 201 obtains encoded three-dimensional data 211 (S201).Next, decoding start GOS determiner 202 determines a current GOS fordecoding (S202). More specifically, decoding start GOS determiner 202refers to meta-information stored in encoded three-dimensional data 211or stored separately from the encoded three-dimensional data todetermine, as the current GOS, a GOS that includes a SPC correspondingto the spatial position, the object, or the time from which decoding isto start.

Next, decoding SPC determiner 203 determines the type(s) (I, P, and/orB) of SPCs to be decoded in the GOS (S203). For example, decoding SPCdeterminer 203 determines whether to (1) decode only I-SPC(s), (2) todecode I-SPC(s) and P-SPCs, or (3) to decode SPCs of all types. Notethat the present step may not be performed, when the type(s) of SPCs tobe decoded are previously determined such as when all SPCs arepreviously determined to be decoded.

Next, decoder 204 obtains an address location within encodedthree-dimensional data 211 from which a SPC that comes first in the GOSin the decoding order (the same as the encoding order) starts. Decoder204 obtains the encoded data of the first SPC from the address location,and sequentially decodes the SPCs from such first SPC (S204). Note thatthe address location is stored in the meta-information, etc.

Three-dimensional data decoding device 200 decodes decodedthree-dimensional data 212 as thus described. More specifically,three-dimensional data decoding device 200 decodes each encodedthree-dimensional data 211 of the first processing units (GOSs), eachbeing a random access unit and being associated with three-dimensionalcoordinates, thereby generating decoded three-dimensional data 212 ofthe first processing units (GOSs). Even more specifically,three-dimensional data decoding device 200 decodes each of the secondprocessing units (SPCs) in each of the first processing units (GOSs).Three-dimensional data decoding device 200 further decodes each of thethird processing units (VLMs) in each of the second processing units(SPCs).

The following describes meta-information for random access. Suchmeta-information is generated by three-dimensional data encoding device100, and included in encoded three-dimensional data 112 (211).

In the conventional random access for a two-dimensional moving picture,decoding starts from the first frame in a random access unit that isclose to a specified time. Meanwhile, in addition to times, randomaccess to spaces (coordinates, objects, etc.) is assumed to be performedin a world.

To enable random access to at least three elements of coordinates,objects, and times, tables are prepared that associate the respectiveelements with the GOS index numbers. Furthermore, the GOS index numbersare associated with the addresses of the respective first I-SPCs in theGOSs. FIG. 10 is a diagram showing example tables included in themeta-information. Note that not all the tables shown in FIG. 10 arerequired to be used, and thus at least one of the tables is used.

The following describes an example in which random access is performedfrom coordinates as a starting point. To access the coordinates (x2, y2,and z2), the coordinates-GOS table is first referred to, which indicatesthat the point corresponding to the coordinates (x2, y2, and z2) isincluded in the second GOS. Next, the GOS-address table is referred to,which indicates that the address of the first I-SPC in the second GOS isaddr(2). As such, decoder 204 obtains data from this address to startdecoding.

Note that the addresses may either be logical addresses or physicaladdresses of an HDD or a memory. Alternatively, information thatidentifies file segments may be used instead of addresses. File segmentsare, for example, units obtained by segmenting at least one GOS, etc.

When an object spans across a plurality of GOSs, the object-GOS tablemay show a plurality of GOSs to which such object belongs. When suchplurality of GOSs are closed GOSs, the encoding device and the decodingdevice can perform encoding or decoding in parallel. Meanwhile, whensuch plurality of GOSs are open GOSs, a higher compression efficiency isachieved by the plurality of GOSs referring to each other.

Example objects include a person, an animal, a car, a bicycle, a signal,and a building serving as a landmark. For example, three-dimensionaldata encoding device 100 extracts keypoints specific to an object from athree-dimensional point cloud, etc., when encoding a world, and detectsthe object on the basis of such keypoints to set the detected object asa random access point.

As thus described, three-dimensional data encoding device 100 generatesfirst information indicating a plurality of first processing units(GOSs) and the three-dimensional coordinates associated with therespective first processing units (GOSs). Encoded three-dimensional data112 (211) includes such first information. The first information furtherindicates at least one of objects, times, and data storage locationsthat are associated with the respective first processing units (GOSs).

Three-dimensional data decoding device 200 obtains the first informationfrom encoded three-dimensional data 211. Using such first information,three-dimensional data decoding device 200 identifies encodedthree-dimensional data 211 of the first processing unit that correspondsto the specified three-dimensional coordinates, object, or time, anddecodes encoded three-dimensional data 211.

The following describes an example of other meta-information. Inaddition to the meta-information for random access, three-dimensionaldata encoding device 100 may also generate and store meta-information asdescribed below, and three-dimensional data decoding device 200 may usesuch meta-information at the time of decoding.

When three-dimensional data is used as map information, for example, aprofile is defined in accordance with the intended use, and informationindicating such profile may be included in meta-information. Forexample, a profile is defined for an urban or a suburban area, or for aflying object, and the maximum or minimum size, etc. of a world, a SPCor a VLM, etc. is defined in each profile. For example, more detailedinformation is required for an urban area than for a suburban area, andthus the minimum VLM size is set to small.

The meta-information may include tag values indicating object types.Each of such tag values is associated with VLMs, SPCs, or GOSs thatconstitute an object. For example, a tag value may be set for eachobject type in a manner, for example, that the tag value “0” indicates“person,” the tag value “1” indicates “car,” and the tag value “2”indicates “signal.” Alternatively, when an object type is hard to judge,or such judgment is not required, a tag value may be used that indicatesthe size or the attribute indicating, for example, whether an object isa dynamic object or a static object.

The meta-information may also include information indicating a range ofthe spatial region occupied by a world.

The meta-information may also store the SPC or V×L size as headerinformation common to the whole stream of the encoded data or to aplurality of SPCs, such as SPCs in a GOS.

The meta-information may also include identification information on adistance sensor or a camera that has been used to generate a pointcloud, or information indicating the positional accuracy of a pointgroup in the point cloud.

The meta-information may also include information indicating whether aworld is made only of static objects or includes a dynamic object.

The following describes variations of the present embodiment.

The encoding device or the decoding device may encode or decode two ormore mutually different SPCs or GOSs in parallel. GOSs to be encoded ordecoded in parallel can be determined on the basis of meta-information,etc. indicating the spatial positions of the GOSs.

When three-dimensional data is used as a spatial map for use by a car ora flying object, etc. in traveling, or for creation of such a spatialmap, for example, the encoding device or the decoding device may encodeor decode GOSs or SPCs included in a space that is identified on thebasis of GPS information, the route information, the zoom magnification,etc.

The decoding device may also start decoding sequentially from a spacethat is close to the self-location or the traveling route. The encodingdevice or the decoding device may give a lower priority to a spacedistant from the self-location or the traveling route than the priorityof a nearby space to encode or decode such distant place. To “give alower priority” means here, for example, to lower the priority in theprocessing sequence, to decrease the resolution (to apply decimation inthe processing), or to lower the image quality (to increase the encodingefficiency by, for example, setting the quantization step to larger).

When decoding encoded data that is hierarchically encoded in a space,the decoding device may decode only the bottom level in the hierarchy.

The decoding device may also start decoding preferentially from thebottom level of the hierarchy in accordance with the zoom magnificationor the intended use of the map.

For self-location estimation or object recognition, etc. involved in theself-driving of a car or a robot, the encoding device or the decodingdevice may encode or decode regions at a lower resolution, except for aregion that is lower than or at a specified height from the ground (theregion to be recognized).

The encoding device may also encode point clouds representing thespatial shapes of a room interior and a room exterior separately. Forexample, the separation of a GOS representing a room interior (interiorGOS) and a GOS representing a room exterior (exterior GOS) enables thedecoding device to select a GOS to be decoded in accordance with aviewpoint location, when using the encoded data.

The encoding device may also encode an interior GOS and an exterior GOShaving close coordinates so that such GOSs come adjacent to each otherin an encoded stream. For example, the encoding device associates theidentifiers of such GOSs with each other, and stores informationindicating the associated identifiers into the meta-information that isstored in the encoded stream or stored separately. This enables thedecoding device to refer to the information in the meta-information toidentify an interior GOS and an exterior GOS having close coordinates.

The encoding device may also change the GOS size or the SPC sizedepending on whether a GOS is an interior GOS or an exterior GOS. Forexample, the encoding device sets the size of an interior GOS to smallerthan the size of an exterior GOS. The encoding device may also changethe accuracy of extracting keypoints from a point cloud, or the accuracyof detecting objects, for example, depending on whether a GOS is aninterior GOS or an exterior GOS.

The encoding device may also add, to encoded data, information by whichthe decoding device displays objects with a distinction between adynamic object and a static object. This enables the decoding device todisplay a dynamic object together with, for example, a red box orletters for explanation. Note that the decoding device may display onlya red box or letters for explanation, instead of a dynamic object. Thedecoding device may also display more particular object types. Forexample, a red box may be used for a car, and a yellow box may be usedfor a person.

The encoding device or the decoding device may also determine whether toencode or decode a dynamic object and a static object as a different SPCor GOS, in accordance with, for example, the appearance frequency ofdynamic objects or a ratio between static objects and dynamic objects.For example, when the appearance frequency or the ratio of dynamicobjects exceeds a threshold, a SPC or a GOS including a mixture of adynamic object and a static object is accepted, while when theappearance frequency or the ratio of dynamic objects is below athreshold, a SPC or GOS including a mixture of a dynamic object and astatic object is unaccepted.

When detecting a dynamic object not from a point cloud but fromtwo-dimensional image information of a camera, the encoding device mayseparately obtain information for identifying a detection result (box orletters) and the object position, and encode these items of informationas part of the encoded three-dimensional data. In such a case, thedecoding device superimposes auxiliary information (box or letters)indicating the dynamic object onto a resultant of decoding a staticobject to display it.

The encoding device may also change the sparseness and denseness of VXLsor VLMs in a SPC in accordance with the degree of complexity of theshape of a static object. For example, the encoding device sets VXLs orVLMs at a higher density as the shape of a static object is morecomplex. The encoding device may further determine a quantization step,etc. for quantizing spatial positions or color information in accordancewith the sparseness and denseness of VXLs or VLMs. For example, theencoding device sets the quantization step to smaller as the density ofVXLs or VLMs is higher.

As described above, the encoding device or the decoding device accordingto the present embodiment encodes or decodes a space on a SPC-by-SPCbasis that includes coordinate information.

Furthermore, the encoding device and the decoding device performencoding or decoding on a volume-by-volume basis in a SPC. Each volumeincludes a voxel, which is the minimum unit in which positioninformation is associated.

Also, using a table that associates the respective elements of spatialinformation including coordinates, objects, and times with GOSs or usinga table that associates these elements with each other, the encodingdevice and the decoding device associate any ones of the elements witheach other to perform encoding or decoding. The decoding device uses thevalues of the selected elements to determine the coordinates, andidentifies a volume, a voxel, or a SPC from such coordinates to decode aSPC including such volume or voxel, or the identified SPC.

Furthermore, the encoding device determines a volume, a voxel, or a SPCthat is selectable in accordance with the elements, through extractionof keypoints and object recognition, and encodes the determined volume,voxel, or SPC, as a volume, a voxel, or a SPC to which random access ispossible.

SPCs are classified into three types: I-SPC that is singly encodable ordecodable; P-SPC that is encoded or decoded by referring to any one ofthe processed SPCs; and B-SPC that is encoded or decoded by referring toany two of the processed SPCs.

At least one volume corresponds to a static object or a dynamic object.A SPC including a static object and a SPC including a dynamic object areencoded or decoded as mutually different GOSs. Stated differently, a SPCincluding a static object and a SPC including a dynamic object areassigned to different GOSs.

Dynamic objects are encoded or decoded on an object-by-object basis, andare associated with at least one SPC including a static object. Stateddifferently, a plurality of dynamic objects are individually encoded,and the obtained encoded data of the dynamic objects is associated witha SPC including a static object.

The encoding device and the decoding device give an increased priorityto I-SPC(s) in a GOS to perform encoding or decoding. For example, theencoding device performs encoding in a manner that prevents thedegradation of I-SPCs (in a manner that enables the originalthree-dimensional data to be reproduced with a higher fidelity afterdecoded). The decoding device decodes, for example, only I-SPCs.

The encoding device may change the frequency of using I-SPCs dependingon the sparseness and denseness or the number (amount) of the objects ina world to perform encoding. Stated differently, the encoding devicechanges the frequency of selecting I-SPCs depending on the number or thesparseness and denseness of the objects included in thethree-dimensional data. For example, the encoding device uses I-SPCs ata higher frequency as the density of the objects in a world is higher.

The encoding device also sets random access points on a GOS-by-GOSbasis, and stores information indicating the spatial regionscorresponding to the GOSs into the header information.

The encoding device uses, for example, a default value as the spatialsize of a GOS. Note that the encoding device may change the GOS sizedepending on the number (amount) or the sparseness and denseness ofobjects or dynamic objects. For example, the encoding device sets thespatial size of a GOS to smaller as the density of objects or dynamicobjects is higher or the number of objects or dynamic objects isgreater.

Also, each SPC or volume includes a keypoint group that is derived byuse of information obtained by a sensor such as a depth sensor, agyroscope sensor, or a camera sensor. The coordinates of the keypointsare set at the central positions of the respective voxels. Furthermore,finer voxels enable highly accurate position information.

The keypoint group is derived by use of a plurality of pictures. Aplurality of pictures include at least two types of time information:the actual time information and the same time information common to aplurality of pictures that are associated with SPCs (for example, theencoding time used for rate control, etc.).

Also, encoding or decoding is performed on a GOS-by-GOS basis thatincludes at least one SPC.

The encoding device and the decoding device predict P-SPCs or B-SPCs ina current GOS by referring to SPCs in a processed GOS.

Alternatively, the encoding device and the decoding device predictP-SPCs or B-SPCs in a current GOS, using the processed SPCs in thecurrent GOS, without referring to a different GOS.

Furthermore, the encoding device and the decoding device transmit orreceive an encoded stream on a world-by-world basis that includes atleast one GOS.

Also, a GOS has a layer structure in one direction at least in a world,and the encoding device and the decoding device start encoding ordecoding from the bottom layer. For example, a random accessible GOSbelongs to the lowermost layer. A GOS that belongs to the same layer ora lower layer is referred to in a GOS that belongs to an upper layer.Stated differently, a GOS is spatially divided in a predetermineddirection in advance to have a plurality of layers, each including atleast one SPC. The encoding device and the decoding device encode ordecode each SPC by referring to a SPC included in the same layer as theeach SPC or a SPC included in a layer lower than that of the each SPC.

Also, the encoding device and the decoding device successively encode ordecode GOSs on a world-by-world basis that includes such GOSs. In sodoing, the encoding device and the decoding device write or read outinformation indicating the order (direction) of encoding or decoding asmetadata. Stated differently, the encoded data includes informationindicating the order of encoding a plurality of GOSs.

The encoding device and the decoding device also encode or decodemutually different two or more SPCs or GOSs in parallel.

Furthermore, the encoding device and the decoding device encode ordecode the spatial information (coordinates, size, etc.) on a SPC or aGOS.

The encoding device and the decoding device encode or decode SPCs orGOSs included in an identified space that is identified on the basis ofexternal information on the self-location or/and region size, such asGPS information, route information, or magnification.

The encoding device or the decoding device gives a lower priority to aspace distant from the self-location than the priority of a nearby spaceto perform encoding or decoding.

The encoding device sets a direction at one of the directions in aworld, in accordance with the magnification or the intended use, toencode a GOS having a layer structure in such direction. Also, thedecoding device decodes a GOS having a layer structure in one of thedirections in a world that has been set in accordance with themagnification or the intended use, preferentially from the bottom layer.

The encoding device changes the accuracy of extracting keypoints, theaccuracy of recognizing objects, or the size of spatial regions, etc.included in a SPC, depending on whether an object is an interior objector an exterior object. Note that the encoding device and the decodingdevice encode or decode an interior GOS and an exterior GOS having closecoordinates in a manner that these GOSs come adjacent to each other in aworld, and associates their identifiers with each other for encoding anddecoding.

Embodiment 2

When using encoded data of a point cloud in an actual device or service,it is desirable that necessary information be transmitted/received inaccordance with the intended use to reduce the network bandwidth.However, there has been no such functionality in the structure ofencoding three-dimensional data, nor an encoding method therefor.

The present embodiment describes a three-dimensional data encodingmethod and a three-dimensional data encoding device for providing thefunctionality of transmitting/receiving only necessary information inencoded data of a three-dimensional point cloud in accordance with theintended use, as well as a three-dimensional data decoding method and athree-dimensional data decoding device for decoding such encoded data.

A voxel (VXL) with a feature greater than or equal to a given amount isdefined as a feature voxel (FVXL), and a world (WLD) constituted byFVXLs is defined as a sparse world (SWLD). FIG. 11 is a diagram showingexample structures of a sparse world and a world. A SWLD includes:FGOSs, each being a GOS constituted by FVXLs; FSPCs, each being a SPCconstituted by FVXLs; and FVLMs, each being a VLM constituted by FVXLs.The data structure and prediction structure of a FGOS, a FSPC, and aFVLM may be the same as those of a GOS, a SPC, and a VLM.

A feature represents the three-dimensional position information on a VXLor the visible-light information on the position of a VXL. A largenumber of features are detected especially at a corner, an edge, etc. ofa three-dimensional object. More specifically, such a feature is athree-dimensional feature or a visible-light feature as described below,but may be any feature that represents the position, luminance, or colorinformation, etc. on a VXL.

Used as three-dimensional features are signature of histograms oforientations (SHOT) features, point feature histograms (PFH) features,or point pair feature (PPF) features.

SHOT features are obtained by dividing the periphery of a VXL, andcalculating an inner product of the reference point and the normalvector of each divided region to represent the calculation result as ahistogram. SHOT features are characterized by a large number ofdimensions and high-level feature representation.

PFH features are obtained by selecting a large number of two point pairsin the vicinity of a VXL, and calculating the normal vector, etc. fromeach two point pair to represent the calculation result as a histogram.PFH features are histogram features, and thus are characterized byrobustness against a certain extent of disturbance and also high-levelfeature representation.

PPF features are obtained by using a normal vector, etc. for each twopoints of VXLs. PPF features, for which all VXLs are used, hasrobustness against occlusion.

Used as visible-light features are scale-invariant feature transform(SIFT), speeded up robust features (SURF), or histogram of orientedgradients (HOG), etc. that use information on an image such as luminancegradient information.

A SWLD is generated by calculating the above-described features of therespective VXLs in a WLD to extract FVXLs. Here, the SWLD may be updatedevery time the WLD is updated, or may be regularly updated after theelapse of a certain period of time, regardless of the timing at whichthe WLD is updated.

A SWLD may be generated for each type of features. For example,different SWLDs may be generated for the respective types of features,such as SWLD1 based on SHOT features and SWLD2 based on SIFT features sothat SWLDs are selectively used in accordance with the intended use.Also, the calculated feature of each FVXL may be held in each FVXL asfeature information.

Next, the usage of a sparse world (SWLD) will be described. A SWLDincludes only feature voxels (FVXLs), and thus its data size is smallerin general than that of a WLD that includes all VXLs.

In an application that utilizes features for a certain purpose, the useof information on a SWLD instead of a WLD reduces the time required toread data from a hard disk, as well as the bandwidth and the timerequired for data transfer over a network. For example, a WLD and a SWLDare held in a server as map information so that map information to besent is selected between the WLD and the SWLD in accordance with arequest from a client. This reduces the network bandwidth and the timerequired for data transfer. More specific examples will be describedbelow;

FIG. 12 and FIG. 13 are diagrams showing usage examples of a SWLD and aWLD. As FIG. 12 shows, when client 1, which is a vehicle-mounted device,requires map information to use it for self-location determination,client 1 sends to a server a request for obtaining map data forself-location estimation (S301). The server sends to client 1 the SWLDin response to the obtainment request (S302). Client 1 uses the receivedSWLD to determine the self-location (S303). In so doing, client 1obtains VXL information on the periphery of client 1 through variousmeans including a distance sensor such as a rangefinder, as well as astereo camera and a combination of a plurality of monocular cameras.Client 1 then estimates the self-location information from the obtainedVXL information and the SWLD. Here, the self-location informationincludes three-dimensional position information, orientation, etc. ofclient 1.

As FIG. 13 shows, when client 2, which is a vehicle-mounted device,requires map information to use it for rendering a map such as athree-dimensional map, client 2 sends to the server a request forobtaining map data for map rendering (S311). The server sends to client2 the WLD in response to the obtainment request (S312). Client 2 usesthe received WLD to render a map (S313). In so doing, client 2 uses, forexample, an image client 2 has captured by a visible-light camera, etc.and the WLD obtained from the server to create a rendering image, andrenders such created image onto a screen of a car navigation system,etc.

As described above, the server sends to a client a SWLD when thefeatures of the respective VXLs are mainly required such as in the caseof self-location estimation, and sends to a client a WLD when detailedVXL information is required such as in the case of map rendering. Thisallows for an efficient sending/receiving of map data.

Note that a client may self-judge which one of a SWLD and a WLD isnecessary, and request the server to send a SWLD or a WLD. Also, theserver may judge which one of a SWLD and a WLD to send in accordancewith the status of the client or a network.

Next, a method will be described of switching the sending/receivingbetween a sparse world (SWLD) and a world (WLD).

Whether to receive a WLD or a SWLD may be switched in accordance withthe network bandwidth. FIG. 14 is a diagram showing an example operationin such case. For example, when a low-speed network is used that limitsthe usable network bandwidth, such as in a Long-Term Evolution (LTE)environment, a client accesses the server over a low-speed network(S321), and obtains the SWLD from the server as map information (S322).Meanwhile, when a high-speed network is used that has an adequatelybroad network bandwidth, such as in a WiFi environment, a clientaccesses the server over a high-speed network (S323), and obtains theWLD from the server (S324). This enables the client to obtainappropriate map information in accordance with the network bandwidthsuch client is using.

More specifically, a client receives the SWLD over an LTE network whenin outdoors, and obtains the WLD over a WiFi network when in indoorssuch as in a facility. This enables the client to obtain more detailedmap information on indoor environment.

As described above, a client may request for a WLD or a SWLD inaccordance with the bandwidth of a network such client is using.Alternatively, the client may send to the server information indicatingthe bandwidth of a network such client is using, and the server may sendto the client data (the WLD or the SWLD) suitable for such client inaccordance with the information. Alternatively, the server may identifythe network bandwidth the client is using, and send to the client data(the WLD or the SWLD) suitable for such client.

Also, whether to receive a WLD or a SWLD may be switched in accordancewith the speed of traveling. FIG. 15 is a diagram showing an exampleoperation in such case. For example, when traveling at a high speed(S331), a client receives the SWLD from the server (S332). Meanwhile,when traveling at a low speed (S333), the client receives the WLD fromthe server (S334). This enables the client to obtain map informationsuitable to the speed, while reducing the network bandwidth. Morespecifically, when traveling on an expressway, the client receives theSWLD with a small data amount, which enables the update of rough mapinformation at an appropriate speed. Meanwhile, when traveling on ageneral road, the client receives the WLD, which enables the obtainmentof more detailed map information.

As described above, the client may request the server for a WLD or aSWLD in accordance with the traveling speed of such client.Alternatively, the client may send to the server information indicatingthe traveling speed of such client, and the server may send to theclient data (the WLD or the SWLD) suitable to such client in accordancewith the information. Alternatively, the server may identify thetraveling speed of the client to send data (the WLD or the SWLD)suitable to such client.

Also, the client may obtain, from the server, a SWLD first, from whichthe client may obtain a WLD of an important region. For example, whenobtaining map information, the client first obtains a SWLD for rough mapinformation, from which the client narrows to a region in which featuressuch as buildings, signals, or persons appear at high frequency so thatthe client can later obtain a WLD of such narrowed region. This enablesthe client to obtain detailed information on a necessary region, whilereducing the amount of data received from the server.

The server may also create from a WLD different SWLDs for the respectiveobjects, and the client may receive SWLDs in accordance with theintended use. This reduces the network bandwidth. For example, theserver recognizes persons or cars in a WLD in advance, and creates aSWLD of persons and a SWLD of cars. The client, when wishing to obtaininformation on persons around the client, receives the SWLD of persons,and when wising to obtain information on cars, receives the SWLD ofcars. Such types of SWLDs may be distinguished by information (flag, ortype, etc.) added to the header, etc.

Next, the structure and the operation flow of the three-dimensional dataencoding device (e.g., a server) according to the present embodimentwill be described. FIG. 16 is a block diagram of three-dimensional dataencoding device 400 according to the present embodiment. FIG. 17 is aflowchart of three-dimensional data encoding processes performed bythree-dimensional data encoding device 400.

Three-dimensional data encoding device 400 shown in FIG. 16 encodesinput three-dimensional data 411, thereby generating encodedthree-dimensional data 413 and encoded three-dimensional data 414, eachbeing an encoded stream. Here, encoded three-dimensional data 413 isencoded three-dimensional data corresponding to a WLD, and encodedthree-dimensional data 414 is encoded three-dimensional datacorresponding to a SWLD. Such three-dimensional data encoding device 400includes, obtainer 401, encoding region determiner 402, SWLD extractor403, WLD encoder 404, and SWLD encoder 405.

First, as FIG. 17 shows, obtainer 401 obtains input three-dimensionaldata 411, which is point group data in a three-dimensional space (S401).

Next, encoding region determiner 402 determines a current spatial regionfor encoding on the basis of a spatial region in which the point clouddata is present (S402).

Next, SWLD extractor 403 defines the current spatial region as a WLD,and calculates the feature from each VXL included in the WLD. Then, SWLDextractor 403 extracts VXLs having an amount of features greater than orequal to a predetermined threshold, defines the extracted VXLs as FVXLs,and adds such FVXLs to a SWLD, thereby generating extractedthree-dimensional data 412 (S403). Stated differently, extractedthree-dimensional data 412 having an amount of features greater than orequal to the threshold is extracted from input three-dimensional data411.

Next, WLD encoder 404 encodes input three-dimensional data 411corresponding to the WLD, thereby generating encoded three-dimensionaldata 413 corresponding to the WLD (S404). In so doing, WLD encoder 404adds to the header of encoded three-dimensional data 413 informationthat distinguishes that such encoded three-dimensional data 413 is astream including a WLD.

SWLD encoder 405 encodes extracted three-dimensional data 412corresponding to the SWLD, thereby generating encoded three-dimensionaldata 414 corresponding to the SWLD (S405). In so doing, SWLD encoder 405adds to the header of encoded three-dimensional data 414 informationthat distinguishes that such encoded three-dimensional data 414 is astream including a SWLD.

Note that the process of generating encoded three-dimensional data 413and the process of generating encoded three-dimensional data 414 may beperformed in the reverse order. Also note that a part or all of theseprocesses may be performed in parallel.

A parameter “world_type” is defined, for example, as information addedto each header of encoded three-dimensional data 413 and encodedthree-dimensional data 414. world_type=0 indicates that a streamincludes a WLD, and world_type=1 indicates that a stream includes aSWLD. An increased number of values may be further assigned to define alarger number of types, e.g., world_type=2. Also, one of encodedthree-dimensional data 413 and encoded three-dimensional data 414 mayinclude a specified flag. For example, encoded three-dimensional data414 may be assigned with a flag indicating that such stream includes aSWLD. In such a case, the decoding device can distinguish whether suchstream is a stream including a WLD or a stream including a SWLD inaccordance with the presence/absence of the flag.

Also, an encoding method used by WLD encoder 404 to encode a WLD may bedifferent from an encoding method used by SWLD encoder 405 to encode aSWLD.

For example, data of a SWLD is decimated, and thus can have a lowercorrelation with the neighboring data than that of a WLD. For thisreason, of intra prediction and inter prediction, inter prediction maybe more preferentially performed in an encoding method used for a SWLDthan in an encoding method used for a WLD.

Also, an encoding method used for a SWLD and an encoding method used fora WLD may represent three-dimensional positions differently. Forexample, three-dimensional coordinates may be used to represent thethree-dimensional positions of FVXLs in a SWLD and an octree describedbelow may be used to represent three-dimensional positions in a WLD, andvice versa.

Also, SWLD encoder 405 performs encoding in a manner that encodedthree-dimensional data 414 of a SWLD has a smaller data size than thedata size of encoded three-dimensional data 413 of a WLD. A SWLD canhave a lower inter-data correlation, for example, than that of a WLD asdescribed above. This can lead to a decreased encoding efficiency, andthus to encoded three-dimensional data 414 having a larger data sizethan the data size of encoded three-dimensional data 413 of a WLD. Whenthe data size of the resulting encoded three-dimensional data 414 islarger than the data size of encoded three-dimensional data 413 of aWLD, SWLD encoder 405 performs encoding again to re-generate encodedthree-dimensional data 414 having a reduced data size.

For example, SWLD extractor 403 re-generates extracted three-dimensionaldata 412 having a reduced number of keypoints to be extracted, and SWLDencoder 405 encodes such extracted three-dimensional data 412.Alternatively, SWLD encoder 405 may perform more coarse quantization.More coarse quantization is achieved, for example, by rounding the datain the lowermost level in an octree structure described below.

When failing to decrease the data size of encoded three-dimensional data414 of the SWLD to smaller than the data size of encodedthree-dimensional data 413 of the WLD. SWLD encoder 405 may not generateencoded three-dimensional data 414 of the SWLD. Alternatively, encodedthree-dimensional data 413 of the WLD may be copied as encodedthree-dimensional data 414 of the SWLD. Stated differently, encodedthree-dimensional data 413 of the WLD may be used as it is as encodedthree-dimensional data 414 of the SWLD.

Next, the structure and the operation flow of the three-dimensional datadecoding device (e.g., a client) according to the present embodimentwill be described. FIG. 18 is a block diagram of three-dimensional datadecoding device 500 according to the present embodiment. FIG. 19 is aflowchart of three-dimensional data decoding processes performed bythree-dimensional data decoding device 500.

Three-dimensional data decoding device 500 shown in FIG. 18 decodesencoded three-dimensional data 511, thereby generating decodedthree-dimensional data 512 or decoded three-dimensional data 513.Encoded three-dimensional data 511 here is, for example, encodedthree-dimensional data 413 or encoded three-dimensional data 414generated by three-dimensional data encoding device 400.

Such three-dimensional data decoding device 500 includes obtainer 501,header analyzer 502, WLD decoder 503, and SWLD decoder 504.

First, as FIG. 19 shows, obtainer 501 obtains encoded three-dimensionaldata 511 (S501). Next, header analyzer 502 analyzes the header ofencoded three-dimensional data 511 to identify whether encodedthree-dimensional data 511 is a stream including a WLD or a streamincluding a SWLD (S602). For example, the above-described parameterworld_type is referred to in making such identification.

When encoded three-dimensional data 511 is a stream including a WLD (Yesin S503), WLD decoder 503 decodes encoded three-dimensional data 511,thereby generating decoded three-dimensional data 512 of the WLD (S604).Meanwhile, when encoded three-dimensional data 511 is a stream includinga SWLD (No in S503), SWLD decoder 504 decodes encoded three-dimensionaldata 511, thereby generating decoded three-dimensional data 513 of theSWLD (S505).

Also, as in the case of the encoding device, a decoding method used byWLD decoder 503 to decode a WLD may be different from a decoding methodused by SWLD decoder 504 to decode a SWLD. For example, of intraprediction and inter prediction, inter prediction may be morepreferentially performed in a decoding method used for a SWLD than in adecoding method used for a WLD.

Also, a decoding method used for a SWLD and a decoding method used for aWLD may represent three-dimensional positions differently. For example,three-dimensional coordinates may be used to represent thethree-dimensional positions of FVXLs in a SWLD and an octree describedbelow may be used to represent three-dimensional positions in a WLD, andvice versa.

Next, an octree representation will be described, which is a method ofrepresenting three-dimensional positions. VXL data included inthree-dimensional data is converted into an octree structure beforeencoded. FIG. 20 is a diagram showing example VXLs in a WLD. FIG. 21 isa diagram showing an octree structure of the WLD shown in FIG. 20. Anexample shown in FIG. 20 illustrates three VXLs 1 to 3 that includepoint groups (hereinafter referred to as effective VXLs). As FIG. 21shows, the octree structure is made of nodes and leaves. Each node has amaximum of eight nodes or leaves. Each leaf has VXL information. Here,of the leaves shown in FIG. 21, leaf 1, leaf 2, and leaf 3 representVXL1, VXL2, and VXL3 shown in FIG. 20, respectively.

More specifically, each node and each leaf correspond to athree-dimensional position. Node 1 corresponds to the entire block shownin FIG. 20. The block that corresponds to node 1 is divided into eightblocks. Of these eight blocks, blocks including effective VXLs are setas nodes, while the other blocks are set as leaves. Each block thatcorresponds to a node is further divided into eight nodes or leaves.These processes are repeated by the number of times that is equal to thenumber of levels in the octree structure. All blocks in the lowermostlevel are set as leaves;

FIG. 22 is a diagram showing an example SWLD generated from the WLDshown in FIG. 20. VXL1 and VXL2 shown in FIG. 20 are judged as FVXL1 andFVXL2 as a result of feature extraction, and thus are added to the SWLD.Meanwhile, VXL3 is not judged as a FVXL, and thus is not added to theSWLD. FIG. 23 is a diagram showing an octree structure of the SWLD shownin FIG. 22. In the octree structure shown in FIG. 23, leaf 3corresponding to VXL3 shown in FIG. 21 is deleted. Consequently, node 3shown in FIG. 21 has lost an effective VXL, and has changed to a leaf.As described above, a SWLD has a smaller number of leaves in generalthan a WLD does, and thus the encoded three-dimensional data of the SWLDis smaller than the encoded three-dimensional data of the WLD.

The following describes variations of the present embodiment.

For self-location estimation, for example, a client, being avehicle-mounted device, etc., may receive a SWLD from the server to usesuch SWLD to estimate the self-location. Meanwhile, for obstacledetection, the client may detect obstacles by use of three-dimensionalinformation on the periphery obtained by such client through variousmeans including a distance sensor such as a rangefinder, as well as astereo camera and a combination of a plurality of monocular cameras.

In general, a SWLD is less likely to include VXL data on a flat region.As such, the server may hold a subsample world (subWLD) obtained bysubsampling a WLD for detection of static obstacles, and send to theclient the SWLD and the subWLD. This enables the client to performself-location estimation and obstacle detection on the client's part,while reducing the network bandwidth.

When the client renders three-dimensional map data at a high speed, mapinformation having a mesh structure is more useful in some cases. Assuch, the server may generate a mesh from a WLD to hold it beforehand asa mesh world (MWLD). For example, when wishing to perform coarsethree-dimensional rendering, the client receives a MWLD, and whenwishing to perform detailed three-dimensional rendering, the clientreceives a WLD. This reduces the network bandwidth.

In the above description, the server sets, as FVXLs, VXLs having anamount of features greater than or equal to the threshold, but theserver may calculate FVXLs by a different method. For example, theserver may judge that a VXL, a VLM, a SPC, or a GOS that constitutes asignal, or an intersection, etc. as necessary for self-locationestimation, driving assist, or self-driving, etc., and incorporate suchVXL, VLM, SPC, or GOS into a SWLD as a FVXL, a FVLM, a FSPC, or a FGOS.Such judgment may be made manually. Also, FVXLs, etc. that have been seton the basis of an amount of features may be added to FVXLs, etc.obtained by the above method. Stated differently, SWLD extractor 403 mayfurther extract, from input three-dimensional data 411, datacorresponding to an object having a predetermined attribute as extractedthree-dimensional data 412.

Also, that a VXL, a VLM, a SPC, or a GOS is necessary for such intendedusage may be labeled separately from the features. The server mayseparately hold, as an upper layer of a SWLD (e.g., a lane world), FVXLsof a signal or an intersection, etc. necessary for self-locationestimation, driving assist, or self-driving, etc.

The server may also add an attribute to VXLs in a WLD on a random accessbasis or on a predetermined unit basis. An attribute, for example,includes information indicating whether VXLs are necessary forself-location estimation, or information indicating whether VXLs areimportant as traffic information such as a signal, or an intersection,etc. An attribute may also include a correspondence between VXLs andfeatures (intersection, or road, etc.) in lane information (geographicdata files (GDF), etc.).

A method as described below may be used to update a WLD or a SWLD.

Update information indicating changes, etc. in a person, a roadwork, ora tree line (for trucks) is uploaded to the server as point groups ormeta data. The server updates a WLD on the basis of such uploadedinformation, and then updates a SWLD by use of the updated WLD.

The client, when detecting a mismatch between the three-dimensionalinformation such client has generated at the time of self-locationestimation and the three-dimensional information received from theserver, may send to the server the three-dimensional information suchclient has generated, together with an update notification. In such acase, the server updates the SWLD by use of the WLD. When the SWLD isnot to be updated, the server judges that the WLD itself is old.

In the above description, information that distinguishes whether anencoded stream is that of a WLD or a SWLD is added as header informationof the encoded stream. However, when there are many types of worlds suchas a mesh world and a lane world, information that distinguishes thesetypes of the worlds may be added to header information. Also, when thereare many SWLDs with different amounts of features, information thatdistinguishes the respective SWLDs may be added to header information.

In the above description, a SWLD is constituted by FVXLs, but a SWLD mayinclude VXLs that have not been judged as FVXLs. For example, a SWLD mayinclude an adjacent VXL used to calculate the feature of a FVXL. Thisenables the client to calculate the feature of a FVXL when receiving aSWLD, even in the case where feature information is not added to eachFVXL of the SWLD. In such a case, the SWLD may include information thatdistinguishes whether each VXL is a FVXL or a VXL.

As described above, three-dimensional data encoding device 400 extracts,from input three-dimensional data 411 (first three-dimensional data),extracted three-dimensional data 412 (second three-dimensional data)having an amount of a feature greater than or equal to a threshold, andencodes extracted three-dimensional data 412 to generate encodedthree-dimensional data 414 (first encoded three-dimensional data).

This three-dimensional data encoding device 400 generates encodedthree-dimensional data 414 that is obtained by encoding data having anamount of a feature greater than or equal to the threshold. This reducesthe amount of data compared to the case where input three-dimensionaldata 411 is encoded as it is. Three-dimensional data encoding device 400is thus capable of reducing the amount of data to be transmitted.

Three-dimensional data encoding device 400 further encodes inputthree-dimensional data 411 to generate encoded three-dimensional data413 (second encoded three-dimensional data).

This three-dimensional data encoding device 400 enables selectivetransmission of encoded three-dimensional data 413 and encodedthree-dimensional data 414, in accordance, for example, with theintended use, etc.

Also, extracted three-dimensional data 412 is encoded by a firstencoding method, and input three-dimensional data 411 is encoded by asecond encoding method different from the first encoding method.

This three-dimensional data encoding device 400 enables the use of anencoding method suitable for each of input three-dimensional data 411and extracted three-dimensional data 412.

Also, of intra prediction and inter prediction, the inter prediction ismore preferentially performed in the first encoding method than in thesecond encoding method.

This three-dimensional data encoding device 400 enables inter predictionto be more preferentially performed on extracted three-dimensional data412 in which adjacent data items are likely to have low correlation.

Also, the first encoding method and the second encoding method representthree-dimensional positions differently. For example, the secondencoding method represents three-dimensional positions by octree, andthe first encoding method represents three-dimensional positions bythree-dimensional coordinates.

This three-dimensional data encoding device 400 enables the use of amore suitable method to represent the three-dimensional positions ofthree-dimensional data in consideration of the difference in the numberof data items (the number of VXLs or FVXLs) included.

Also, at least one of encoded three-dimensional data 413 and encodedthree-dimensional data 414 includes an identifier indicating whether theencoded three-dimensional data is encoded three-dimensional dataobtained by encoding input three-dimensional data 411 or encodedthree-dimensional data obtained by encoding part of inputthree-dimensional data 411. Stated differently, such identifierindicates whether the encoded three-dimensional data is encodedthree-dimensional data 413 of a WLD or encoded three-dimensional data414 of a SWLD.

This enables the decoding device to readily judge whether the obtainedencoded three-dimensional data is encoded three-dimensional data 413 orencoded three-dimensional data 414.

Also, three-dimensional data encoding device 400 encodes extractedthree-dimensional data 412 in a manner that encoded three-dimensionaldata 414 has a smaller data amount than a data amount of encodedthree-dimensional data 413.

This three-dimensional data encoding device 400 enables encodedthree-dimensional data 414 to have a smaller data amount than the dataamount of encoded three-dimensional data 413.

Also, three-dimensional data encoding device 400 further extracts datacorresponding to an object having a predetermined attribute from inputthree-dimensional data 411 as extracted three-dimensional data 412. Theobject having a predetermined attribute is, for example, an objectnecessary for self-location estimation, driving assist, or self-driving,etc., or more specifically, a signal, an intersection, etc.

This three-dimensional data encoding device 400 is capable of generatingencoded three-dimensional data 414 that includes data required by thedecoding device.

Also, three-dimensional data encoding device 400 (server) further sends,to a client, one of encoded three-dimensional data 413 and encodedthree-dimensional data 414 in accordance with a status of the client.

This three-dimensional data encoding device 400 is capable of sendingappropriate data in accordance with the status of the client.

Also, the status of the client includes one of a communication condition(e.g., network bandwidth) of the client and a traveling speed of theclient.

Also, three-dimensional data encoding device 400 further sends, to aclient, one of encoded three-dimensional data 413 and encodedthree-dimensional data 414 in accordance with a request from the client.

This three-dimensional data encoding device 400 is capable of sendingappropriate data in accordance with the request from the client.

Also, three-dimensional data decoding device 500 according to thepresent embodiment decodes encoded three-dimensional data 413 or encodedthree-dimensional data 414 generated by three-dimensional data encodingdevice 400 described above.

Stated differently, three-dimensional data decoding device 500 decodes,by a first decoding method, encoded three-dimensional data 414 obtainedby encoding extracted three-dimensional data 412 having an amount of afeature greater than or equal to a threshold, extractedthree-dimensional data 412 having been extracted from inputthree-dimensional data 411. Three-dimensional data decoding device 500also decodes, by a second decoding method, encoded three-dimensionaldata 413 obtained by encoding input three-dimensional data 411, thesecond decoding method being different from the first decoding method.

This three-dimensional data decoding device 500 enables selectivereception of encoded three-dimensional data 414 obtained by encodingdata having an amount of a feature greater than or equal to thethreshold and encoded three-dimensional data 413, in accordance, forexample, with the intended use, etc. Three-dimensional data decodingdevice 500 is thus capable of reducing the amount of data to betransmitted. Such three-dimensional data decoding device 500 furtherenables the use of a decoding method suitable for each of inputthree-dimensional data 411 and extracted three-dimensional data 412.

Also, of intra prediction and inter prediction, the inter prediction ismore preferentially performed in the first decoding method than in thesecond decoding method.

This three-dimensional data decoding device 500 enables inter predictionto be more preferentially performed on the extracted three-dimensionaldata in which adjacent data items are likely to have low correlation.

Also, the first decoding method and the second decoding method representthree-dimensional positions differently. For example, the seconddecoding method represents three-dimensional positions by octree, andthe first decoding method represents three-dimensional positions bythree-dimensional coordinates.

This three-dimensional data decoding device 500 enables the use of amore suitable method to represent the three-dimensional positions ofthree-dimensional data in consideration of the difference in the numberof data items (the number of VXLs or FVXLs) included.

Also, at least one of encoded three-dimensional data 413 and encodedthree-dimensional data 414 includes an identifier indicating whether theencoded three-dimensional data is encoded three-dimensional dataobtained by encoding input three-dimensional data 411 or encodedthree-dimensional data obtained by encoding part of inputthree-dimensional data 411. Three-dimensional data decoding device 500refers to such identifier in identifying between encodedthree-dimensional data 413 and encoded three-dimensional data 414.

This three-dimensional data decoding device 500 is capable of readilyjudging whether the obtained encoded three-dimensional data is encodedthree-dimensional data 413 or encoded three-dimensional data 414.

Three-dimensional data decoding device 500 further notifies a server ofa status of the client (three-dimensional data decoding device 500).Three-dimensional data decoding device 500 receives one of encodedthree-dimensional data 413 and encoded three-dimensional data 414 fromthe server, in accordance with the status of the client.

This three-dimensional data decoding device 500 is capable of receivingappropriate data in accordance with the status of the client.

Also, the status of the client includes one of a communication condition(e.g., network bandwidth) of the client and a traveling speed of theclient.

Three-dimensional data decoding device 500 further makes a request ofthe server for one of encoded three-dimensional data 413 and encodedthree-dimensional data 414, and receives one of encodedthree-dimensional data 413 and encoded three-dimensional data 414 fromthe server, in accordance with the request.

This three-dimensional data decoding device 500 is capable of receivingappropriate data in accordance with the intended use.

Embodiment 3

The present embodiment will describe a method of transmitting/receivingthree-dimensional data between vehicles. For example, thethree-dimensional data is transmitted/received between the own vehicleand the nearby vehicle;

FIG. 24 is a block diagram of three-dimensional data creation device 620according to the present embodiment. Such three-dimensional datacreation device 620, which is included, for example, in the own vehicle,mergers first three-dimensional data 632 created by three-dimensionaldata creation device 620 with the received second three-dimensional data635, thereby creating third three-dimensional data 636 having a higherdensity.

Such three-dimensional data creation device 620 includesthree-dimensional data creator 621, request range determiner 622,searcher 623, receiver 624, decoder 625, and merger 626.

First, three-dimensional data creator 621 creates firstthree-dimensional data 632 by use of sensor information 631 detected bythe sensor included in the own vehicle. Next, request range determiner622 determines a request range, which is the range of athree-dimensional space, the data on which is insufficient in thecreated first three-dimensional data 632.

Next, searcher 623 searches for the nearby vehicle having thethree-dimensional data of the request range, and sends request rangeinformation 633 indicating the request range to nearby vehicle 601having been searched out (S623). Next, receiver 624 receives encodedthree-dimensional data 634, which is an encoded stream of the requestrange, from nearby vehicle 601 (S624). Note that searcher 623 mayindiscriminately send requests to all vehicles included in a specifiedrange to receive encoded three-dimensional data 634 from a vehicle thathas responded to the request. Searcher 623 may send a request not onlyto vehicles but also to an object such as a signal and a sign, andreceive encoded three-dimensional data 634 from the object.

Next, decoder 625 decodes the received encoded three-dimensional data634, thereby obtaining second three-dimensional data 635. Next, merger626 merges first three-dimensional data 632 with secondthree-dimensional data 635, thereby creating three-dimensional data 636having a higher density.

Next, the structure and operations of three-dimensional datatransmission device 640 according to the present embodiment will bedescribed. FIG. 25 is a block diagram of three-dimensional datatransmission device 640.

Three-dimensional data transmission device 640 is included, for example,in the above-described nearby vehicle. Three-dimensional datatransmission device 640 processes fifth three-dimensional data 652created by the nearby vehicle into sixth three-dimensional data 654requested by the own vehicle, encodes sixth three-dimensional data 654to generate encoded three-dimensional data 634, and sends encodedthree-dimensional data 634 to the own vehicle.

Three-dimensional data transmission device 640 includesthree-dimensional data creator 641, receiver 642, extractor 643, encoder644, and transmitter 645.

First, three-dimensional data creator 641 creates fifththree-dimensional data 652 by use of sensor information 651 detected bythe sensor included in the nearby vehicle. Next, receiver 642 receivesrequest range information 633 from the own vehicle.

Next, extractor 643 extracts from fifth three-dimensional data 652 thethree-dimensional data of the request range indicated by request rangeinformation 633, thereby processing fifth three-dimensional data 652into sixth three-dimensional data 654. Next, encoder 644 encodes sixththree-dimensional data 654 to generate encoded three-dimensional data643, which is an encoded stream. Then, transmitter 645 sends encodedthree-dimensional data 634 to the own vehicle.

Note that although an example case is described here in which the ownvehicle includes three-dimensional data creation device 620 and thenearby vehicle includes three-dimensional data transmission device 640,each of the vehicles may include the functionality of boththree-dimensional data creation device 620 and three-dimensional datatransmission device 640.

Embodiment 4

The present embodiment describes operations performed in abnormal caseswhen self-location estimation is performed on the basis of athree-dimensional map.

A three-dimensional map is expected to find its expanded use inself-driving of a vehicle and autonomous movement, etc. of a mobileobject such as a robot and a flying object (e.g., a drone). Examplemeans for enabling such autonomous movement include a method in which amobile object travels in accordance with a three-dimensional map, whileestimating its self-location on the map (self-location estimation).

The self-location estimation is enabled by matching a three-dimensionalmap with three-dimensional information on the surrounding of the ownvehicle (hereinafter referred to as self-detected three-dimensionaldata) obtained by a sensor equipped in the own vehicle, such as arangefinder (e.g., a LiDAR) and a stereo camera to estimate the locationof the own vehicle on the three-dimensional map.

As in the case of an HD map suggested by HERE Technologies, for example,a three-dimensional map may include not only a three-dimensional pointcloud, but also two-dimensional map data such as information on theshapes of roads and intersections, or information that changes inreal-time such as information on a traffic jam and an accident. Athree-dimensional map includes a plurality of layers such as layers ofthree-dimensional data, two-dimensional data, and meta-data that changesin real-time, from among which the device can obtain or refer to onlynecessary data.

Point cloud data may be a SWLD as described above, or may include pointgroup data that is different from keypoints. The transmission/receptionof point cloud data is basically carried out in one or more randomaccess units.

A method described below is used as a method of matching athree-dimensional map with self-detected three-dimensional data. Forexample, the device compares the shapes of the point groups in eachother's point clouds, and determines that portions having a high degreeof similarity among keypoints correspond to the same position. When thethree-dimensional map is formed by a SWLD, the device also performsmatching by comparing the keypoints that form the SWLD withthree-dimensional keypoints extracted from the self-detectedthree-dimensional data.

Here, to enable highly accurate self-location estimation, the followingneeds to be satisfied: (A) the three-dimensional map and theself-detected three-dimensional data have been already obtained; and (B)their accuracies satisfy a predetermined requirement. However, one of(A) and (B) cannot be satisfied in abnormal cases such as ones describedbelow.

1. A three-dimensional map is unobtainable over communication.

2. A three-dimensional map is not present, or a three-dimensional maphaving been obtained is corrupt.

3. A sensor of the own vehicle has trouble, or the accuracy of thegenerated self-detected three-dimensional data is inadequate due to badweather.

The following describes operations to cope with such abnormal cases. Thefollowing description illustrates an example case of a vehicle, but themethod described below is applicable to mobile objects on the whole thatare capable of autonomous movement, such as a robot and a drone.

The following describes the structure of the three-dimensionalinformation processing device and its operation according to the presentembodiment capable of coping with abnormal cases regarding athree-dimensional map or self-detected three-dimensional data. FIG. 26is a block diagram of an example structure of three-dimensionalinformation processing device 700 according to the present embodiment.

Three-dimensional information processing device 700 is equipped, forexample, in a mobile object such as a car. As shown in FIG. 26,three-dimensional information processing device 700 includesthree-dimensional map obtainer 701, self-detected data obtainer 702,abnormal case judgment unit 703, coping operation determiner 704, andoperation controller 705.

Note that three-dimensional information processing device 700 mayinclude a non-illustrated two-dimensional or one-dimensional sensor thatdetects a structural object or a mobile object around the own vehicle,such as a camera capable of obtaining two-dimensional images and asensor for one-dimensional data utilizing ultrasonic or laser.Three-dimensional information processing device 700 may also include anon-illustrated communication unit that obtains a three-dimensional mapover a mobile communication network, such as 4G and 5G, or viainter-vehicle communication or road-to-vehicle communication.

Three-dimensional map obtainer 701 obtains three-dimensional map 711 ofthe surroundings of the traveling route. For example, three-dimensionalmap obtainer 701 obtains three-dimensional map 711 over a mobilecommunication network, or via inter-vehicle communication orroad-to-vehicle communication.

Next, self-detected data obtainer 702 obtains self-detectedthree-dimensional data 712 on the basis of sensor information. Forexample, self-detected data obtainer 702 generates self-detectedthree-dimensional data 712 on the basis of the sensor informationobtained by a sensor equipped in the own vehicle.

Next, abnormal case judgment unit 703 conducts a predetermined check ofat least one of obtained three-dimensional map 711 and self-detectedthree-dimensional data 712 to detect an abnormal case. Stateddifferently, abnormal case judgment unit 703 judges whether at least oneof obtained three-dimensional map 711 and self-detectedthree-dimensional data 712 is abnormal.

When the abnormal case is detected, coping operation determiner 704determines a coping operation to cope with such abnormal case. Next,operation controller 705 controls the operation of each of theprocessing units necessary to perform the coping operation.

Meanwhile, when no abnormal case is detected, three-dimensionalinformation processing device 700 terminates the process.

Also, three-dimensional information processing device 700 estimates thelocation of the vehicle equipped with three-dimensional informationprocessing device 700, using three-dimensional map 711 and self-detectedthree-dimensional data 712. Next, three-dimensional informationprocessing device 700 performs the automatic operation of the vehicle byuse of the estimated location of the vehicle.

As described above, three-dimensional information processing device 700obtains, via a communication channel, map data (three-dimensional map711) that includes first three-dimensional position information. Thefirst three-dimensional position information includes, for example, aplurality of random access units, each of which is an assembly of atleast one subspace and is individually decodable, the at least onesubspace having three-dimensional coordinates information and serving asa unit in which each of the plurality of random access units is encoded.The first three-dimensional position information is, for example, data(SWLD) obtained by encoding keypoints, each of which has an amount of athree-dimensional feature greater than or equal to a predeterminedthreshold.

Three-dimensional information processing device 700 also generatessecond three-dimensional position information (self-detectedthree-dimensional data 712) from information detected by a sensor.Three-dimensional information processing device 700 then judges whetherone of the first three-dimensional position information and the secondthree-dimensional position information is abnormal by performing, on oneof the first three-dimensional position information and the secondthree-dimensional position information, a process of judging whether anabnormality is present.

Three-dimensional information processing device 700 determines a copingoperation to cope with the abnormality when one of the firstthree-dimensional position information and the second three-dimensionalposition information is judged to be abnormal. Three-dimensionalinformation processing device 700 then executes a control that isrequired to perform the coping operation.

This structure enables three-dimensional information processing device700 to detect an abnormality regarding one of the firstthree-dimensional position information and the second three-dimensionalposition information, and to perform a coping operation therefor.

Embodiment 5

The present embodiment describes a method, etc. of transmittingthree-dimensional data to a following vehicle;

FIG. 27 is a block diagram of an exemplary structure ofthree-dimensional data creation device 810 according to the presentembodiment. Such three-dimensional data creation device 810 is equipped,for example, in a vehicle. Three-dimensional data creation device 810transmits and receives three-dimensional data to and from an externalcloud-based traffic monitoring system, a preceding vehicle, or afollowing vehicle, and creates and stores three-dimensional data.

Three-dimensional data creation device 810 includes data receiver 811,communication unit 812, reception controller 813, format converter 814,a plurality of sensors 815, three-dimensional data creator 816,three-dimensional data synthesizer 817, three-dimensional data storage818, communication unit 819, transmission controller 820, formatconverter 821, and data transmitter 822.

Data receiver 811 receives three-dimensional data 831 from a cloud-basedtraffic monitoring system or a preceding vehicle. Three-dimensional data831 includes, for example, information on a region undetectable bysensors 815 of the own vehicle, such as a point cloud, visible lightvideo, depth information, sensor position information, and speedinformation.

Communication unit 812 communicates with the cloud-based trafficmonitoring system or the preceding vehicle to transmit a datatransmission request, etc. to the cloud-based traffic monitoring systemor the preceding vehicle.

Reception controller 813 exchanges information, such as information onsupported formats, with a communications partner via communication unit812 to establish communication with the communications partner.

Format converter 814 applies format conversion, etc. onthree-dimensional data 831 received by data receiver 811 to generatethree-dimensional data 832. Format converter 814 also decompresses ordecodes three-dimensional data 831 when three-dimensional data 831 iscompressed or encoded.

A plurality of sensors 815 are a group of sensors, such as visible lightcameras and infrared cameras, that obtain information on the outside ofthe vehicle and generate sensor information 833. Sensor information 833is, for example, three-dimensional data such as a point cloud (pointgroup data), when sensors 815 are laser sensors such as LiDARs. Notethat a single sensor may serve as a plurality of sensors 815.

Three-dimensional data creator 816 generates three-dimensional data 834from sensor information 833. Three-dimensional data 834 includes, forexample, information such as a point cloud, visible light video, depthinformation, sensor position information, and speed information.

Three-dimensional data synthesizer 817 synthesizes three-dimensionaldata 834 created on the basis of sensor information 833 of the ownvehicle with three-dimensional data 832 created by the cloud-basedtraffic monitoring system or the preceding vehicle, etc., therebyforming three-dimensional data 835 of a space that includes the spaceahead of the preceding vehicle undetectable by sensors 815 of the ownvehicle.

Three-dimensional data storage 818 stores generated three-dimensionaldata 835, etc.

Communication unit 819 communicates with the cloud-based trafficmonitoring system or the following vehicle to transmit a datatransmission request, etc. to the cloud-based traffic monitoring systemor the following vehicle.

Transmission controller 820 exchanges information such as information onsupported formats with a communications partner via communication unit819 to establish communication with the communications partner.

Transmission controller 820 also determines a transmission region, whichis a space of the three-dimensional data to be transmitted, on the basisof three-dimensional data formation information on three-dimensionaldata 832 generated by three-dimensional data synthesizer 817 and thedata transmission request from the communications partner.

More specifically, transmission controller 820 determines a transmissionregion that includes the space ahead of the own vehicle undetectable bya sensor of the following vehicle, in response to the data transmissionrequest from the cloud-based traffic monitoring system or the followingvehicle. Transmission controller 820 judges, for example, whether aspace is transmittable or whether the already transmitted space includesan update, on the basis of the three-dimensional data formationinformation to determine a transmission region. For example,transmission controller 820 determines, as a transmission region, aregion that is: a region specified by the data transmission request; anda region, corresponding three-dimensional data 835 of which is present.Transmission controller 820 then notifies format converter 821 of theformat supported by the communications partner and the transmissionregion.

Of three-dimensional data 835 stored in three-dimensional data storage818, format converter 821 converts three-dimensional data 836 of thetransmission region into the format supported by the receiver end togenerate three-dimensional data 837. Note that format converter 821 maycompress or encode three-dimensional data 837 to reduce the data amount.

Data transmitter 822 transmits three-dimensional data 837 to thecloud-based traffic monitoring system or the following vehicle. Suchthree-dimensional data 837 includes, for example, information on a blindspot, which is a region hidden from view of the following vehicle, suchas a point cloud ahead of the own vehicle, visible light video, depthinformation, and sensor position information.

Note that an example has been described in which format converter 814and format converter 821 perform format conversion, etc., but formatconversion may not be performed.

With the above structure, three-dimensional data creation device 810obtains, from an external device, three-dimensional data 831 of a regionundetectable by sensors 815 of the own vehicle, and synthesizesthree-dimensional data 831 with three-dimensional data 834 that is basedon sensor information 833 detected by sensors 815 of the own vehicle,thereby generating three-dimensional data 835. Three-dimensional datacreation device 810 is thus capable of generating three-dimensional dataof a range undetectable by sensors 815 of the own vehicle.

Three-dimensional data creation device 810 is also capable oftransmitting, to the cloud-based traffic monitoring system or thefollowing vehicle, etc., three-dimensional data of a space that includesthe space ahead of the own vehicle undetectable by a sensor of thefollowing vehicle, in response to the data transmission request from thecloud-based traffic monitoring system or the following vehicle.

Embodiment 6

In embodiment 5, an example is described in which a client device of avehicle or the like transmits three-dimensional data to another vehicleor a server such as a cloud-based traffic monitoring system. In thepresent embodiment, a client device transmits sensor informationobtained through a sensor to a server or a client device.

A structure of a system according to the present embodiment will firstbe described. FIG. 28 is a diagram showing the structure of atransmission/reception system of a three-dimensional map and sensorinformation according to the present embodiment. This system includesserver 901, and client devices 902A and 902B. Note that client devices902A and 902B are also referred to as client device 902 when noparticular distinction is made therebetween.

Client device 902 is, for example, a vehicle-mounted device equipped ina mobile object such as a vehicle. Server 901 is, for example, acloud-based traffic monitoring system, and is capable of communicatingwith the plurality of client devices 902.

Server 901 transmits the three-dimensional map formed by a point cloudto client device 902. Note that a structure of the three-dimensional mapis not limited to a point cloud, and may also be another structureexpressing three-dimensional data such as a mesh structure.

Client device 902 transmits the sensor information obtained by clientdevice 902 to server 901. The sensor information includes, for example,at least one of information obtained by LiDAR, a visible light image, aninfrared image, a depth image, sensor position information, or sensorspeed information.

The data to be transmitted and received between server 901 and clientdevice 902 may be compressed in order to reduce data volume, and mayalso be transmitted uncompressed in order to maintain data precision.When compressing the data, it is possible to use a three-dimensionalcompression method on the point cloud based on, for example, an octreestructure. It is possible to use a two-dimensional image compressionmethod on the visible light image, the infrared image, and the depthimage. The two-dimensional image compression method is, for example,MPEG-4 AVC or HEVC standardized by MPEG.

Server 901 transmits the three-dimensional map managed by server 901 toclient device 902 in response to a transmission request for thethree-dimensional map from client device 902. Note that server 901 mayalso transmit the three-dimensional map without waiting for thetransmission request for the three-dimensional map from client device902. For example, server 901 may broadcast the three-dimensional map toat least one client device 902 located in a predetermined space. Server901 may also transmit the three-dimensional map suited to a position ofclient device 902 at fixed time intervals to client device 902 that hasreceived the transmission request once. Server 901 may also transmit thethree-dimensional map managed by server 901 to client device 902 everytime the three-dimensional map is updated.

Client device 902 sends the transmission request for thethree-dimensional map to server 901. For example, when client device 902wants to perform the self-location estimation during traveling, clientdevice 902 transmits the transmission request for the three-dimensionalmap to server 901.

Note that in the following cases, client device 902 may send thetransmission request for the three-dimensional map to server 901. Clientdevice 902 may send the transmission request for the three-dimensionalmap to server 901 when the three-dimensional map stored by client device902 is old. For example, client device 902 may send the transmissionrequest for the three-dimensional map to server 901 when a fixed periodhas passed since the three-dimensional map is obtained by client device902.

Client device 902 may also send the transmission request for thethree-dimensional map to server 901 before a fixed time when clientdevice 902 exits a space shown in the three-dimensional map stored byclient device 902. For example, client device 902 may send thetransmission request for the three-dimensional map to server 901 whenclient device 902 is located within a predetermined distance from aboundary of the space shown in the three-dimensional map stored byclient device 902. When a movement path and a movement speed of clientdevice 902 are understood, a time when client device 902 exits the spaceshown in the three-dimensional map stored by client device 902 may bepredicted based on the movement path and the movement speed of clientdevice 902.

Client device 902 may also send the transmission request for thethree-dimensional map to server 901 when an error during alignment ofthe three-dimensional data and the three-dimensional map created fromthe sensor information by client device 902 is at least at a fixedlevel.

Client device 902 transmits the sensor information to server 901 inresponse to a transmission request for the sensor information fromserver 901. Note that client device 902 may transmit the sensorinformation to server 901 without waiting for the transmission requestfor the sensor information from server 901. For example, client device902 may periodically transmit the sensor information during a fixedperiod when client device 902 has received the transmission request forthe sensor information from server 901 once. Client device 902 maydetermine that there is a possibility of a change in thethree-dimensional map of a surrounding area of client device 902 havingoccurred, and transmit this information and the sensor information toserver 901, when the error during alignment of the three-dimensionaldata created by client device 902 based on the sensor information andthe three-dimensional map obtained from server 901 is at least at thefixed level.

Server 901 sends a transmission request for the sensor information toclient device 902. For example, server 901 receives positioninformation, such as GPS information, about client device 902 fromclient device 902. Server 901 sends the transmission request for thesensor information to client device 902 in order to generate a newthree-dimensional map, when it is determined that client device 902 isapproaching a space in which the three-dimensional map managed by server901 contains little information, based on the position information aboutclient device 902. Server 901 may also send the transmission request forthe sensor information, when wanting to (i) update the three-dimensionalmap, (ii) check road conditions during snowfall, a disaster, or thelike, or (iii) check traffic congestion conditions, accident/incidentconditions, or the like.

Client device 902 may set an amount of data of the sensor information tobe transmitted to server 901 in accordance with communication conditionsor bandwidth during reception of the transmission request for the sensorinformation to be received from server 901. Setting the amount of dataof the sensor information to be transmitted to server 901 is, forexample, increasing/reducing the data itself or appropriately selectinga compression method;

FIG. 29 is a block diagram showing an example structure of client device902. Client device 902 receives the three-dimensional map formed by apoint cloud and the like from server 901, and estimates a self-locationof client device 902 using the three-dimensional map created based onthe sensor information of client device 902. Client device 902 transmitsthe obtained sensor information to server 901.

Client device 902 includes data receiver 1011, communication unit 1012,reception controller 1013, format converter 1014, sensors 1015,three-dimensional data creator 1016, three-dimensional image processor1017, three-dimensional data storage 1018, format converter 1019,communication unit 1020, transmission controller 1021, and datatransmitter 1022.

Data receiver 1011 receives three-dimensional map 1031 from server 901.Three-dimensional map 1031 is data that includes a point cloud such as aWLD or a SWLD. Three-dimensional map 1031 may include compressed data oruncompressed data.

Communication unit 1012 communicates with server 901 and transmits adata transmission request (e.g. transmission request forthree-dimensional map) to server 901.

Reception controller 1013 exchanges information, such as information onsupported formats, with a communications partner via communication unit1012 to establish communication with the communications partner.

Format converter 1014 performs a format conversion and the like onthree-dimensional map 1031 received by data receiver 1011 to generatethree-dimensional map 1032. Format converter 1014 also performs adecompression or decoding process when three-dimensional map 1031 iscompressed or encoded. Note that format converter 1014 does not performthe decompression or decoding process when three-dimensional map 1031 isuncompressed data.

Sensors 815 are a group of sensors, such as LiDARs, visible lightcameras, infrared cameras, or depth sensors that obtain informationabout the outside of a vehicle equipped with client device 902, andgenerate sensor information 1033. Sensor information 1033 is, forexample, three-dimensional data such as a point cloud (point group data)when sensors 1015 are laser sensors such as LiDARs. Note that a singlesensor may serve as sensors 1015.

Three-dimensional data creator 1016 generates three-dimensional data1034 of a surrounding area of the own vehicle based on sensorinformation 1033. For example, three-dimensional data creator 1016generates point cloud data with color information on the surroundingarea of the own vehicle using information obtained by LiDAR and visiblelight video obtained by a visible light camera.

Three-dimensional image processor 1017 performs a self-locationestimation process and the like of the own vehicle, using (i) thereceived three-dimensional map 1032 such as a point cloud, and (ii)three-dimensional data 1034 of the surrounding area of the own vehiclegenerated using sensor information 1033. Note that three-dimensionalimage processor 1017 may generate three-dimensional data 1035 about thesurroundings of the own vehicle by merging three-dimensional map 1032and three-dimensional data 1034, and may perform the self-locationestimation process using the created three-dimensional data 1035.

Three-dimensional data storage 1018 stores three-dimensional map 1032,three-dimensional data 1034, three-dimensional data 1035, and the like.

Format converter 1019 generates sensor information 1037 by convertingsensor information 1033 to a format supported by a receiver end. Notethat format converter 1019 may reduce the amount of data by compressingor encoding sensor information 1037. Format converter 1019 may omit thisprocess when format conversion is not necessary. Format converter 1019may also control the amount of data to be transmitted in accordance witha specified transmission range.

Communication unit 1020 communicates with server 901 and receives a datatransmission request (transmission request for sensor information) andthe like from server 901.

Transmission controller 1021 exchanges information, such as informationon supported formats, with a communications partner via communicationunit 1020 to establish communication with the communications partner.

Data transmitter 1022 transmits sensor information 1037 to server 901.Sensor information 1037 includes, for example, information obtainedthrough sensors 1015, such as information obtained by LiDAR, a luminanceimage obtained by a visible light camera, an infrared image obtained byan infrared camera, a depth image obtained by a depth sensor, sensorposition information, and sensor speed information.

A structure of server 901 will be described next. FIG. 30 is a blockdiagram showing an example structure of server 901. Server 901 transmitssensor information from client device 902 and creates three-dimensionaldata based on the received sensor information. Server 901 updates thethree-dimensional map managed by server 901 using the createdthree-dimensional data. Server 901 transmits the updatedthree-dimensional map to client device 902 in response to a transmissionrequest for the three-dimensional map from client device 902.

Server 901 includes data receiver 1111, communication unit 1112,reception controller 1113, format converter 1114, three-dimensional datacreator 1116, three-dimensional data merger 1117, three-dimensional datastorage 1118, format converter 1119, communication unit 1120,transmission controller 1121, and data transmitter 1122.

Data receiver 1111 receives sensor information 1037 from client device902. Sensor information 1037 includes, for example, information obtainedby LiDAR, a luminance image obtained by a visible light camera, aninfrared image obtained by an infrared camera, a depth image obtained bya depth sensor, sensor position information, sensor speed information,and the like.

Communication unit 1112 communicates with client device 902 andtransmits a data transmission request (e.g. transmission request forsensor information) and the like to client device 902.

Reception controller 1113 exchanges information, such as information onsupported formats, with a communications partner via communication unit1112 to establish communication with the communications partner.

Format converter 1114 generates sensor information 1132 by performing adecompression or decoding process when the received sensor information1037 is compressed or encoded. Note that format converter 1114 does notperform the decompression or decoding process when sensor information1037 is uncompressed data.

Three-dimensional data creator 1116 generates three-dimensional data1134 of a surrounding area of client device 902 based on sensorinformation 1132. For example, three-dimensional data creator 1116generates point cloud data with color information on the surroundingarea of client device 902 using information obtained by LiDAR andvisible light video obtained by a visible light camera.

Three-dimensional data merger 1117 updates three-dimensional map 1135 bymerging three-dimensional data 1134 created based on sensor information1132 with three-dimensional map 1135 managed by server 901.

Three-dimensional data storage 1118 stores three-dimensional map 1135and the like.

Format converter 1119 generates three-dimensional map 1031 by convertingthree-dimensional map 1135 to a format supported by the receiver end.Note that format converter 1119 may reduce the amount of data bycompressing or encoding three-dimensional map 1135. Format converter1119 may omit this process when format conversion is not necessary.Format converter 1119 may also control the amount of data to betransmitted in accordance with a specified transmission range.

Communication unit 1120 communicates with client device 902 and receivesa data transmission request (transmission request for three-dimensionalmap) and the like from client device 902.

Transmission controller 1121 exchanges information, such as informationon supported formats, with a communications partner via communicationunit 1120 to establish communication with the communications partner.

Data transmitter 1122 transmits three-dimensional map 1031 to clientdevice 902. Three-dimensional map 1031 is data that includes a pointcloud such as a WLD or a SWLD. Three-dimensional map 1031 may includeone of compressed data and uncompressed data.

An operational flow of client device 902 will be described next. FIG. 31is a flowchart of an operation when client device 902 obtains thethree-dimensional map.

Client device 902 first requests server 901 to transmit thethree-dimensional map (point cloud, etc.) (S1001). At this point, byalso transmitting the position information about client device 902obtained through GPS and the like, client device 902 may also requestserver 901 to transmit a three-dimensional map relating to this positioninformation.

Client device 902 next receives the three-dimensional map from server901 (S1002). When the received three-dimensional map is compressed data,client device 902 decodes the received three-dimensional map andgenerates an uncompressed three-dimensional map (S1003).

Client device 902 next creates three-dimensional data 1034 of thesurrounding area of client device 902 using sensor information 1033obtained by sensors 1015 (S1004). Client device 902 next estimates theself-location of client device 902 using three-dimensional map 1032received from server 901 and three-dimensional data 1034 created usingsensor information 1033 (S1005);

FIG. 32 is a flowchart of an operation when client device 902 transmitsthe sensor information. Client device 902 first receives a transmissionrequest for the sensor information from server 901 (S1011). Clientdevice 902 that has received the transmission request transmits sensorinformation 1037 to server 901 (S1012). Note that client device 902 maygenerate sensor information 1037 by compressing each piece ofinformation using a compression method suited to each piece ofinformation, when sensor information 1033 includes a plurality of piecesof information obtained by sensors 1015.

An operational flow of server 901 will be described next. FIG. 33 is aflowchart of an operation when server 901 obtains the sensorinformation. Server 901 first requests client device 902 to transmit thesensor information (S1021). Server 901 next receives sensor information1037 transmitted from client device 902 in accordance with the request(S1022). Server 901 next creates three-dimensional data 1134 using thereceived sensor information 1037 (S1023). Server 901 next reflects thecreated three-dimensional data 1134 in three-dimensional map 1135(S1024);

FIG. 34 is a flowchart of an operation when server 901 transmits thethree-dimensional map. Server 901 first receives a transmission requestfor the three-dimensional map from client device 902 (S1031). Server 901that has received the transmission request for the three-dimensional maptransmits the three-dimensional map to client device 902 (S1032). Atthis point, server 901 may extract a three-dimensional map of a vicinityof client device 902 along with the position information about clientdevice 902, and transmit the extracted three-dimensional map. Server 901may compress the three-dimensional map formed by a point cloud using,for example, an octree structure compression method, and transmit thecompressed three-dimensional map.

Hereinafter, variations of the present embodiment will be described.

Server 901 creates three-dimensional data 1134 of a vicinity of aposition of client device 902 using sensor information 1037 receivedfrom client device 902. Server 901 next calculates a difference betweenthree-dimensional data 1134 and three-dimensional map 1135, by matchingthe created three-dimensional data 1134 with three-dimensional map 1135of the same area managed by server 901. Server 901 determines that atype of anomaly has occurred in the surrounding area of client device902, when the difference is greater than or equal to a predeterminedthreshold. For example, it is conceivable that a large difference occursbetween three-dimensional map 1135 managed by server 901 andthree-dimensional data 1134 created based on sensor information 1037,when land subsidence and the like occurs due to a natural disaster suchas an earthquake.

Sensor information 1037 may include information indicating at least oneof a sensor type, a sensor performance, and a sensor model number.Sensor information 1037 may also be appended with a class ID and thelike in accordance with the sensor performance. For example, when sensorinformation 1037 is obtained by LiDAR, it is conceivable to assignidentifiers to the sensor performance. A sensor capable of obtaininginformation with precision in units of several millimeters is class 1, asensor capable of obtaining information with precision in units ofseveral centimeters is class 2, and a sensor capable of obtaininginformation with precision in units of several meters is class 3. Server901 may estimate sensor performance information and the like from amodel number of client device 902. For example, when client device 902is equipped in a vehicle, server 901 may determine sensor specificationinformation from a type of the vehicle. In this case, server 901 mayobtain information on the type of the vehicle in advance, and theinformation may also be included in the sensor information. Server 901may change a degree of correction with respect to three-dimensional data1134 created using sensor information 1037, using the obtained sensorinformation 1037. For example, when the sensor performance is high inprecision (class 1), server 901 does not correct three-dimensional data1134. When the sensor performance is low in precision (class 3), server901 corrects three-dimensional data 1134 in accordance with theprecision of the sensor. For example, server 901 increases the degree(intensity) of correction with a decrease in the precision of thesensor.

Server 901 may simultaneously send the transmission request for thesensor information to the plurality of client devices 902 in a certainspace. Server 901 does not need to use all of the sensor information forcreating three-dimensional data 1134 and may, for example, select sensorinformation to be used in accordance with the sensor performance, whenhaving received a plurality of pieces of sensor information from theplurality of client devices 902. For example, when updatingthree-dimensional map 1135, server 901 may select high-precision sensorinformation (class 1) from among the received plurality of pieces ofsensor information, and create three-dimensional data 1134 using theselected sensor information.

Server 901 is not limited to only being a server such as a cloud-basedtraffic monitoring system, and may also be another (vehicle-mounted)client device. FIG. 35 is a diagram of a system structure in this case.

For example, client device 902C sends a transmission request for sensorinformation to client device 902A located nearby, and obtains the sensorinformation from client device 902A. Client device 902C then createsthree-dimensional data using the obtained sensor information of clientdevice 902A, and updates a three-dimensional map of client device 902C.This enables client device 902C to generate a three-dimensional map of aspace that can be obtained from client device 902A, and fully utilizethe performance of client device 902C. For example, such a case isconceivable when client device 902C has high performance.

In this case, client device 902A that has provided the sensorinformation is given rights to obtain the high-precisionthree-dimensional map generated by client device 902C. Client device902A receives the high-precision three-dimensional map from clientdevice 902C in accordance with these rights.

Server 901 may send the transmission request for the sensor informationto the plurality of client devices 902 (client device 902A and clientdevice 902B) located nearby client device 902C. When a sensor of clientdevice 902A or client device 902B has high performance, client device902C is capable of creating the three-dimensional data using the sensorinformation obtained by this high-performance sensor;

FIG. 36 is a block diagram showing a functionality structure of server901 and client device 902. Server 901 includes, for example,three-dimensional map compression/decoding processor 1201 thatcompresses and decodes the three-dimensional map and sensor informationcompression/decoding processor 1202 that compresses and decodes thesensor information.

Client device 902 includes three-dimensional map decoding processor 1211and sensor information compression processor 1212. Three-dimensional mapdecoding processor 1211 receives encoded data of the compressedthree-dimensional map, decodes the encoded data, and obtains thethree-dimensional map. Sensor information compression processor 1212compresses the sensor information itself instead of thethree-dimensional data created using the obtained sensor information,and transmits the encoded data of the compressed sensor information toserver 901. With this structure, client device 902 does not need tointernally store a processor that performs a process for compressing thethree-dimensional data of the three-dimensional map (point cloud, etc.),as long as client device 902 internally stores a processor that performsa process for decoding the three-dimensional map (point cloud, etc.).This makes it possible to limit costs, power consumption, and the likeof client device 902.

As stated above, client device 902 according to the present embodimentis equipped in the mobile object, and creates three-dimensional data1034 of a surrounding area of the mobile object using sensor information1033 that is obtained through sensor 1015 equipped in the mobile objectand indicates a surrounding condition of the mobile object. Clientdevice 902 estimates a self-location of the mobile object using thecreated three-dimensional data 1034. Client device 902 transmits theobtained sensor information 1033 to server 901 or another mobile object.

This enables client device 902 to transmit sensor information 1033 toserver 901 or the like. This makes it possible to further reduce theamount of transmission data compared to when transmitting thethree-dimensional data. Since there is no need for client device 902 toperform processes such as compressing or encoding the three-dimensionaldata, it is possible to reduce the processing amount of client device902. As such, client device 902 is capable of reducing the amount ofdata to be transmitted or simplifying the structure of the device.

Client device 902 further transmits the transmission request for thethree-dimensional map to server 901 and receives three-dimensional map1031 from server 901. In the estimating of the self-location, clientdevice 902 estimates the self-location using three-dimensional data 1034and three-dimensional map 1032.

Sensor information 1034 includes at least one of information obtained bya laser sensor, a luminance image, an infrared image, a depth image,sensor position information, or sensor speed information.

Sensor information 1033 includes information that indicates aperformance of the sensor.

Client device 902 encodes or compresses sensor information 1033, and inthe transmitting of the sensor information, transmits sensor information1037 that has been encoded or compressed to server 901 or another mobileobject 902. This enables client device 902 to reduce the amount of datato be transmitted.

For example, client device 902 includes a processor and memory. Theprocessor performs the above processes using the memory.

Server 901 according to the present embodiment is capable ofcommunicating with client device 902 equipped in the mobile object, andreceives sensor information 1037 that is obtained through sensor 1015equipped in the mobile object and indicates a surrounding condition ofthe mobile object. Server 901 creates three-dimensional data 1134 of asurrounding area of the mobile object using the received sensorinformation 1037.

With this, server 901 creates three-dimensional data 1134 using sensorinformation 1037 transmitted from client device 902. This makes itpossible to further reduce the amount of transmission data compared towhen client device 902 transmits the three-dimensional data. Since thereis no need for client device 902 to perform processes such ascompressing or encoding the three-dimensional data, it is possible toreduce the processing amount of client device 902. As such, server 901is capable of reducing the amount of data to be transmitted orsimplifying the structure of the device.

Server 901 further transmits a transmission request for the sensorinformation to client device 902.

Server 901 further updates three-dimensional map 1135 using the createdthree-dimensional data 1134, and transmits three-dimensional map 1135 toclient device 902 in response to the transmission request forthree-dimensional map 1135 from client device 902.

Sensor information 1037 includes at least one of information obtained bya laser sensor, a luminance image, an infrared image, a depth image,sensor position information, or sensor speed information.

Sensor information 1037 includes information that indicates aperformance of the sensor.

Server 901 further corrects the three-dimensional data in accordancewith the performance of the sensor. This enables the three-dimensionaldata creation method to improve the quality of the three-dimensionaldata.

In the receiving of the sensor information, server 901 receives aplurality of pieces of sensor information 1037 received from a pluralityof client devices 902, and selects sensor information 1037 to be used inthe creating of three-dimensional data 1134, based on a plurality ofpieces of information that each indicates the performance of the sensorincluded in the plurality of pieces of sensor information 1037. Thisenables server 901 to improve the quality of three-dimensional data1134.

Server 901 decodes or decompresses the received sensor information 1037,and creates three-dimensional data 1134 using sensor information 1132that has been decoded or decompressed. This enables server 901 to reducethe amount of data to be transmitted.

For example, server 901 includes a processor and memory. The processorperforms the above processes using the memory.

Embodiment 7

In the present embodiment, three-dimensional data encoding and decodingmethods using an inter prediction process will be described;

FIG. 37 is a block diagram of three-dimensional data encoding device1300 according to the present embodiment. This three-dimensional dataencoding device 1300 generates an encoded bitstream (hereinafter, alsosimply referred to as bitstream) that is an encoded signal, by encodingthree-dimensional data. As illustrated in FIG. 37, three-dimensionaldata encoding device 1300 includes divider 1301, subtractor 1302,transformer 1303, quantizer 1304, inverse quantizer 1305, inversetransformer 1306, adder 1307, reference volume memory 1308, intrapredictor 1309, reference space memory 1310, inter predictor 1311,prediction controller 1312, and entropy encoder 1313.

Divider 1301 divides a plurality of volumes (VLMs) that are encodingunits of each space (SPC) included in the three-dimensional data.Divider 1301 makes an octree representation (make into an octree) ofvoxels in each volume. Note that divider 1301 may make the spaces intoan octree representation with the spaces having the same size as thevolumes. Divider 1301 may also append information (depth information,etc.) necessary for making the octree representation to a header and thelike of a bitstream.

Subtractor 1302 calculates a difference between a volume (encodingtarget volume) outputted by divider 1301 and a predicted volumegenerated through intra prediction or inter prediction, which will bedescribed later, and outputs the calculated difference to transformer1303 as a prediction residual. FIG. 38 is a diagram showing an examplecalculation of the prediction residual. Note that bit sequences of theencoding target volume and the predicted volume shown here are, forexample, position information indicating positions of three-dimensionalpoints included in the volumes.

Hereinafter, a scan order of an octree representation and voxels will bedescribed. A volume is encoded after being converted into an octreestructure (made into an octree). The octree structure includes nodes andleaves. Each node has eight nodes or leaves, and each leaf has voxel(VXL) information. FIG. 39 is a diagram showing an example structure ofa volume including voxels. FIG. 40 is a diagram showing an example ofthe volume shown in FIG. 39 having been converted into the octreestructure. Among the leaves shown in FIG. 40, leaves 1, 2, and 3respectively represent VXL 1, VXL 2, and VXL 3, and represent VXLsincluding a point group (hereinafter, active VXLs).

An octree is represented by, for example, binary sequences of 1s and 0s.For example, when giving the nodes or the active VXLs a value of 1 andeverything else a value of 0, each node and leaf is assigned with thebinary sequence shown in FIG. 40. Thus, this binary sequence is scannedin accordance with a breadth-first or a depth-first scan order. Forexample, when scanning breadth-first, the binary sequence shown in A ofFIG. 41 is obtained. When scanning depth-first, the binary sequenceshown in B of FIG. 41 is obtained. The binary sequences obtained throughthis scanning are encoded through entropy encoding, which reduces anamount of information.

Depth information in the octree representation will be described next.Depth in the octree representation is used in order to control up to howfine a granularity point cloud information included in a volume isstored. Upon setting a great depth, it is possible to reproduce thepoint cloud information to a more precise level, but an amount of datafor representing the nodes and leaves increases. Upon setting a smalldepth, however, the amount of data decreases, but some information thatthe point cloud information originally held is lost, since pieces ofpoint cloud information including different positions and differentcolors are now considered as pieces of point cloud information includingthe same position and the same color.

For example, FIG. 42 is a diagram showing an example in which the octreewith a depth of 2 shown in FIG. 40 is represented with a depth of 1. Theoctree shown in FIG. 42 has a lower amount of data than the octree shownin FIG. 40. In other words, the binarized octree shown in FIG. 42 has alower bit count than the octree shown in FIG. 40. Leaf 1 and leaf 2shown in FIG. 40 are represented by leaf 1 shown in FIG. 41. In otherwords, the information on leaf 1 and leaf 2 being in different positionsis lost;

FIG. 43 is a diagram showing a volume corresponding to the octree shownin FIG. 42. VXL 1 and VXL 2 shown in FIG. 39 correspond to VXL 12 shownin FIG. 43. In this case, three-dimensional data encoding device 1300generates color information of VXL 12 shown in FIG. 43 using colorinformation of VXL 1 and VXL 2 shown in FIG. 39. For example,three-dimensional data encoding device 1300 calculates an average value,a median, a weighted average value, or the like of the color informationof VXL 1 and VXL 2 as the color information of VXL 12. In this manner,three-dimensional data encoding device 1300 may control a reduction ofthe amount of data by changing the depth of the octree.

Three-dimensional data encoding device 1300 may set the depthinformation of the octree to units of worlds, units of spaces, or unitsof volumes. In this case, three-dimensional data encoding device 1300may append the depth information to header information of the world,header information of the space, or header information of the volume. Inall worlds, spaces, and volumes associated with different times, thesame value may be used as the depth information. In this case,three-dimensional data encoding device 1300 may append the depthinformation to header information managing the worlds associated withall times.

When the color information is included in the voxels, transformer 1303applies frequency transformation, e.g. orthogonal transformation, to aprediction residual of the color information of the voxels in thevolume. For example, transformer 1303 creates a one-dimensional array byscanning the prediction residual in a certain scan order. Subsequently,transformer 1303 transforms the one-dimensional array to a frequencydomain by applying one-dimensional orthogonal transformation to thecreated one-dimensional array. With this, when a value of the predictionresidual in the volume is similar, a value of a low-frequency componentincreases and a value of a high-frequency component decreases. As such,it is possible to more efficiently reduce an encoding amount inquantizer 1304.

Transformer 1303 does not need to use orthogonal transformation in onedimension, but may also use orthogonal transformation in two or moredimensions. For example, transformer 1303 maps the prediction residualto a two-dimensional array in a certain scan order, and appliestwo-dimensional orthogonal transformation to the obtainedtwo-dimensional array. Transformer 1303 may select an orthogonaltransformation method to be used from a plurality of orthogonaltransformation methods. In this case, three-dimensional data encodingdevice 1300 appends, to the bitstream, information indicating whichorthogonal transformation method is used. Transformer 1303 may select anorthogonal transformation method to be used from a plurality oforthogonal transformation methods in different dimensions. In this case,three-dimensional data encoding device 1300 appends, to the bitstream,in how many dimensions the orthogonal transformation method is used.

For example, transformer 1303 matches the scan order of the predictionresidual to a scan order (breadth-first, depth-first, or the like) inthe octree in the volume. This makes it possible to reduce overhead,since information indicating the scan order of the prediction residualdoes not need to be appended to the bitstream. Transformer 1303 mayapply a scan order different from the scan order of the octree. In thiscase, three-dimensional data encoding device 1300 appends, to thebitstream, information indicating the scan order of the predictionresidual. This enables three-dimensional data encoding device 1300 toefficiently encode the prediction residual. Three-dimensional dataencoding device 1300 may append, to the bitstream, information (flag,etc.) indicating whether to apply the scan order of the octree, and mayalso append, to the bitstream, information indicating the scan order ofthe prediction residual when the scan order of the octree is notapplied.

Transformer 1303 does not only transform the prediction residual of thecolor information, and may also transform other attribute informationincluded in the voxels. For example, transformer 1303 may transform andencode information, such as reflectance information, obtained whenobtaining a point cloud through LiDAR and the like.

Transformer 1303 may skip these processes when the spaces do not includeattribute information such as color information. Three-dimensional dataencoding device 1300 may append, to the bitstream, information (flag)indicating whether to skip the processes of transformer 1303.

Quantizer 1304 generates a quantized coefficient by performingquantization using a quantization control parameter on a frequencycomponent of the prediction residual generated by transformer 1303. Withthis, the amount of information is further reduced. The generatedquantized coefficient is outputted to entropy encoder 1313. Quantizer1304 may control the quantization control parameter in units of worlds,units of spaces, or units of volumes. In this case, three-dimensionaldata encoding device 1300 appends the quantization control parameter toeach header information and the like. Quantizer 1304 may performquantization control by changing a weight per frequency component of theprediction residual. For example, quantizer 1304 may precisely quantizea low-frequency component and roughly quantize a high-frequencycomponent. In this case, three-dimensional data encoding device 1300 mayappend, to a header, a parameter expressing a weight of each frequencycomponent.

Quantizer 1304 may skip these processes when the spaces do not includeattribute information such as color information. Three-dimensional dataencoding device 1300 may append, to the bitstream, information (flag)indicating whether to skip the processes of quantizer 1304.

Inverse quantizer 1305 generates an inverse quantized coefficient of theprediction residual by performing inverse quantization on the quantizedcoefficient generated by quantizer 1304 using the quantization controlparameter, and outputs the generated inverse quantized coefficient toinverse transformer 1306.

Inverse transformer 1306 generates an inverse transformation-appliedprediction residual by applying inverse transformation on the inversequantized coefficient generated by inverse quantizer 1305. This inversetransformation-applied prediction residual does not need to completelycoincide with the prediction residual outputted by transformer 1303,since the inverse transformation-applied prediction residual is aprediction residual that is generated after the quantization.

Adder 1307 adds, to generate a reconstructed volume, (i) the inversetransformation-applied prediction residual generated by inversetransformer 1306 to (ii) a predicted volume that is generated throughintra prediction or intra prediction, which will be described later, andis used to generate a pre-quantized prediction residual. Thisreconstructed volume is stored in reference volume memory 1308 orreference space memory 1310.

Intra predictor 1309 generates a predicted volume of an encoding targetvolume using attribute information of a neighboring volume stored inreference volume memory 1308. The attribute information includes colorinformation or a reflectance of the voxels. Intra predictor 1309generates a predicted value of color information or a reflectance of theencoding target volume;

FIG. 44 is a diagram for describing an operation of intra predictor1309. For example, intra predictor 1309 generates the predicted volumeof the encoding target volume (volume idx=3) shown in FIG. 44, using aneighboring volume (volume idx=0). Volume idx here is identifierinformation that is appended to a volume in a space, and a differentvalue is assigned to each volume. An order of assigning volume idx maybe the same as an encoding order, and may also be different from theencoding order. For example, intra predictor 1309 uses an average valueof color information of voxels included in volume idx=0, which is aneighboring volume, as the predicted value of the color information ofthe encoding target volume shown in FIG. 44. In this case, a predictionresidual is generated by deducting the predicted value of the colorinformation from the color information of each voxel included in theencoding target volume. The following processes are performed bytransformer 1303 and subsequent processors with respect to thisprediction residual. In this case, three-dimensional data encodingdevice 1300 appends, to the bitstream, neighboring volume informationand prediction mode information. The neighboring volume information hereis information indicating a neighboring volume used in the prediction,and indicates, for example, volume idx of the neighboring volume used inthe prediction. The prediction mode information here indicates a modeused to generate the predicted volume. The mode is, for example, anaverage value mode in which the predicted value is generated using anaverage value of the voxels in the neighboring volume, or a median modein which the predicted value is generated using the median of the voxelsin the neighboring volume.

Intra predictor 1309 may generate the predicted volume using a pluralityof neighboring volumes. For example, in the structure shown in FIG. 44,intra predictor 1309 generates predicted volume 0 using a volume withvolume idx=0, and generates predicted volume 1 using a volume withvolume idx=1. Intra predictor 1309 then generates an average ofpredicted volume 0 and predicted volume 1 as a final predicted volume.In this case, three-dimensional data encoding device 1300 may append, tothe bitstream, a plurality of volumes idx of a plurality of volumes usedto generate the predicted volume;

FIG. 45 is a diagram schematically showing the inter prediction processaccording to the present embodiment. Inter predictor 1311 encodes (interpredicts) a space (SPC) associated with certain time T_Cur using anencoded space associated with different time T_LX. In this case, interpredictor 1311 performs an encoding process by applying a rotation andtranslation process to the encoded space associated with different timeT_LX.

Three-dimensional data encoding device 1300 appends, to the bitstream,RT information relating to a rotation and translation process suited tothe space associated with different time T_LX. Different time T_LX is,for example, time T_L0 before certain time T_Cur. At this point,three-dimensional data encoding device 1300 may append, to thebitstream, RT information RT_L0 relating to a rotation and translationprocess suited to a space associated with time T_L0.

Alternatively, different time T_LX is, for example, time T_L1 aftercertain time T_Cur. At this point, three-dimensional data encodingdevice 1300 may append, to the bitstream, RT information RT_L1 relatingto a rotation and translation process suited to a space associated withtime T_L1.

Alternatively, inter predictor 1311 encodes (bidirectional prediction)with reference to the spaces associated with time T_L0 and time T_L1that differ from each other. In this case, three-dimensional dataencoding device 1300 may append, to the bitstream, both RT informationRT_L0 and RT information RT_L1 relating to the rotation and translationprocess suited to the spaces thereof.

Note that T_L0 has been described as being before T_Cur and T_L1 asbeing after T_Cur, but are not necessarily limited thereto. For example,T_L0 and T_L1 may both be before T_Cur. T_L0 and T_L1 may also both beafter T_Cur.

Three-dimensional data encoding device 1300 may append, to thebitstream, RT information relating to a rotation and translation processsuited to spaces associated with different times, when encoding withreference to each of the spaces. For example, three-dimensional dataencoding device 1300 manages a plurality of encoded spaces to bereferred to, using two reference lists (list L0 and list L1). When afirst reference space in list L0 is L0R0, a second reference space inlist L0 is L0R, a first reference space in list L1 is L1R0, and a secondreference space in list L1 is L1R1, three-dimensional data encodingdevice 1300 appends, to the bitstream, RT information RT_L0R0 of L0R0,RT information RT_L0R1 of L0R1, RT information RT_L1R0 of L1R0, and RTinformation RT_L1R1 of L1R1. For example, three-dimensional dataencoding device 1300 appends these pieces of RT information to a headerand the like of the bitstream.

Three-dimensional data encoding device 1300 determines whether to applyrotation and translation per reference space, when encoding withreference to reference spaces associated with different times. In thiscase, three-dimensional data encoding device 1300 may append, to headerinformation and the like of the bitstream, information (RT flag, etc.)indicating whether rotation and translation are applied per referencespace. For example, three-dimensional data encoding device 1300calculates the RT information and an Iterative Closest Point (ICP) errorvalue, using an ICP algorithm per reference space to be referred to fromthe encoding target space. Three-dimensional data encoding device 1300determines that rotation and translation do not need to be performed andsets the RT flag to OFF, when the ICP error value is lower than or equalto a predetermined fixed value. In contrast, three-dimensional dataencoding device 1300 sets the RT flag to ON and appends the RTinformation to the bitstream, when the ICP error value exceeds the abovefixed value;

FIG. 46 is a diagram showing an example syntax to be appended to aheader of the RT information and the RT flag. Note that a bit countassigned to each syntax may be decided based on a range of this syntax.For example, when eight reference spaces are included in reference listL0, 3 bits may be assigned to MaxRefSpc_l0. The bit count to be assignedmay be variable in accordance with a value each syntax can be, and mayalso be fixed regardless of the value each syntax can be. When the bitcount to be assigned is fixed, three-dimensional data encoding device1300 may append this fixed bit count to other header information.

MaxRefSpc_l0 shown in FIG. 46 indicates a number of reference spacesincluded in reference list L0. RT_flag_l0[i] is an RT flag of referencespace i in reference list L0. When RT_flag_l0[i] is 1, rotation andtranslation are applied to reference space i. When RT_flag_l0[i] is 0,rotation and translation are not applied to reference space i.

R_l0[i] and T_l0[i] are RT information of reference space i in referencelist L0. R_l0[i] is rotation information of reference space i inreference list L0. The rotation information indicates contents of theapplied rotation process, and is, for example, a rotation matrix or aquaternion. T_l0[i] is translation information of reference space i inreference list L0. The translation information indicates contents of theapplied translation process, and is, for example, a translation vector.

MaxRefSpc_l1 indicates a number of reference spaces included inreference list L1. RT_flag_l1[i] is an RT flag of reference space i inreference list L1. When RT_flag_l1[i] is 1, rotation and translation areapplied to reference space i. When RT_flag_l1[i] is 0, rotation andtranslation are not applied to reference space i.

R_l1[i] and T_l1[i] are RT information of reference space i in referencelist L1. R_l1[i] is rotation information of reference space i inreference list L1. The rotation information indicates contents of theapplied rotation process, and is, for example, a rotation matrix or aquaternion. T_l1[i] is translation information of reference space i inreference list L1. The translation information indicates contents of theapplied translation process, and is, for example, a translation vector.

Inter predictor 1311 generates the predicted volume of the encodingtarget volume using information on an encoded reference space stored inreference space memory 1310. As stated above, before generating thepredicted volume of the encoding target volume, inter predictor 1311calculates RT information at an encoding target space and a referencespace using an ICP algorithm, in order to approach an overall positionalrelationship between the encoding target space and the reference space.Inter predictor 1311 then obtains reference space B by applying arotation and translation process to the reference space using thecalculated RT information. Subsequently, inter predictor 1311 generatesthe predicted volume of the encoding target volume in the encodingtarget space using information in reference space B. Three-dimensionaldata encoding device 1300 appends, to header information and the like ofthe encoding target space, the RT information used to obtain referencespace B.

In this manner, inter predictor 1311 is capable of improving precisionof the predicted volume by generating the predicted volume using theinformation of the reference space, after approaching the overallpositional relationship between the encoding target space and thereference space, by applying a rotation and translation process to thereference space. It is possible to reduce the encoding amount since itis possible to limit the prediction residual. Note that an example hasbeen described in which ICP is performed using the encoding target spaceand the reference space, but is not necessarily limited thereto. Forexample, inter predictor 1311 may calculate the RT information byperforming ICP using at least one of (i) an encoding target space inwhich a voxel or point cloud count is pruned, or (ii) a reference spacein which a voxel or point cloud count is pruned, in order to reduce theprocessing amount.

When the ICP error value obtained as a result of the ICP is smaller thana predetermined first threshold, i.e., when for example the positionalrelationship between the encoding target space and the reference spaceis similar, inter predictor 1311 determines that a rotation andtranslation process is not necessary, and the rotation and translationprocess does not need to be performed. In this case, three-dimensionaldata encoding device 1300 may control the overhead by not appending theRT information to the bitstream.

When the ICP error value is greater than a predetermined secondthreshold, inter predictor 1311 determines that a shape change betweenthe spaces is large, and intra prediction may be applied on all volumesof the encoding target space. Hereinafter, spaces to which intraprediction is applied will be referred to as intra spaces. The secondthreshold is greater than the above first threshold. The presentembodiment is not limited to ICP, and any type of method may be used aslong as the method calculates the RT information using two voxel sets ortwo point cloud sets.

When attribute information, e.g. shape or color information, is includedin the three-dimensional data, inter predictor 1311 searches, forexample, a volume whose attribute information, e.g. shape or colorinformation, is the most similar to the encoding target volume in thereference space, as the predicted volume of the encoding target volumein the encoding target space. This reference space is, for example, areference space on which the above rotation and translation process hasbeen performed. Inter predictor 1311 generates the predicted volumeusing the volume (reference volume) obtained through the search. FIG. 47is a diagram for describing a generating operation of the predictedvolume. When encoding the encoding target volume (volume idx=0) shown inFIG. 47 using inter prediction, inter predictor 1311 searches a volumewith a smallest prediction residual, which is the difference between theencoding target volume and the reference volume, while sequentiallyscanning the reference volume in the reference space. Inter predictor1311 selects the volume with the smallest prediction residual as thepredicted volume. The prediction residuals of the encoding target volumeand the predicted volume are encoded through the processes performed bytransformer 1303 and subsequent processors. The prediction residual hereis a difference between the attribute information of the encoding targetvolume and the attribute information of the predicted volume.Three-dimensional data encoding device 1300 appends, to the header andthe like of the bitstream, volume idx of the reference volume in thereference space, as the predicted volume.

In the example shown in FIG. 47, the reference volume with volume idx=4of reference space L0R0 is selected as the predicted volume of theencoding target volume. The prediction residuals of the encoding targetvolume and the reference volume, and reference volume idx=4 are thenencoded and appended to the bitstream.

Note that an example has been described in which the predicted volume ofthe attribute information is generated, but the same process may beapplied to the predicted volume of the position information.

Prediction controller 1312 controls whether to encode the encodingtarget volume using intra prediction or inter prediction. A modeincluding intra prediction and inter prediction is referred to here as aprediction mode. For example, prediction controller 1312 calculates theprediction residual when the encoding target volume is predicted usingintra prediction and the prediction residual when the encoding targetvolume is predicted using inter prediction as evaluation values, andselects the prediction mode whose evaluation value is smaller. Note thatprediction controller 1312 may calculate an actual encoding amount byapplying orthogonal transformation, quantization, and entropy encodingto the prediction residual of the intra prediction and the predictionresidual of the inter prediction, and select a prediction mode using thecalculated encoding amount as the evaluation value. Overhead information(reference volume idx information, etc.) aside from the predictionresidual may be added to the evaluation value. Prediction controller1312 may continuously select intra prediction when it has been decidedin advance to encode the encoding target space using intra space.

Entropy encoder 1313 generates an encoded signal (encoded bitstream) byvariable-length encoding the quantized coefficient, which is an inputfrom quantizer 1304. To be specific, entropy encoder 1313, for example,binarizes the quantized coefficient and arithmetically encodes theobtained binary signal.

A three-dimensional data decoding device that decodes the encoded signalgenerated by three-dimensional data encoding device 1300 will bedescribed next. FIG. 48 is a block diagram of three-dimensional datadecoding device 1400 according to the present embodiment. Thisthree-dimensional data decoding device 1400 includes entropy decoder1401, inverse quantizer 1402, inverse transformer 1403, adder 1404,reference volume memory 1405, intra predictor 1406, reference spacememory 1407, inter predictor 1408, and prediction controller 1409.

Entropy decoder 1401 variable-length decodes the encoded signal (encodedbitstream). For example, entropy decoder 1401 generates a binary signalby arithmetically decoding the encoded signal, and generates a quantizedcoefficient using the generated binary signal.

Inverse quantizer 1402 generates an inverse quantized coefficient byinverse quantizing the quantized coefficient inputted from entropydecoder 1401, using a quantization parameter appended to the bitstreamand the like.

Inverse transformer 1403 generates a prediction residual by inversetransforming the inverse quantized coefficient inputted from inversequantizer 1402. For example, inverse transformer 1403 generates theprediction residual by inverse orthogonally transforming the inversequantized coefficient, based on information appended to the bitstream.

Adder 1404 adds, to generate a reconstructed volume, (i) the predictionresidual generated by inverse transformer 1403 to (ii) a predictedvolume generated through intra prediction or intra prediction. Thisreconstructed volume is outputted as decoded three-dimensional data andis stored in reference volume memory 1405 or reference space memory1407.

Intra predictor 1406 generates a predicted volume through intraprediction using a reference volume in reference volume memory 1405 andinformation appended to the bitstream. To be specific, intra predictor1406 obtains neighboring volume information (e.g. volume idx) appendedto the bitstream and prediction mode information, and generates thepredicted volume through a mode indicated by the prediction modeinformation, using a neighboring volume indicated in the neighboringvolume information. Note that the specifics of these processes are thesame as the above-mentioned processes performed by intra predictor 1309,except for which information appended to the bitstream is used.

Inter predictor 1408 generates a predicted volume through interprediction using a reference space in reference space memory 1407 andinformation appended to the bitstream. To be specific, inter predictor1408 applies a rotation and translation process to the reference spaceusing the RT information per reference space appended to the bitstream,and generates the predicted volume using the rotated and translatedreference space. Note that when an RT flag is present in the bitstreamper reference space, inter predictor 1408 applies a rotation andtranslation process to the reference space in accordance with the RTflag. Note that the specifics of these processes are the same as theabove-mentioned processes performed by inter predictor 1311, except forwhich information appended to the bitstream is used.

Prediction controller 1409 controls whether to decode a decoding targetvolume using intra prediction or inter prediction. For example,prediction controller 1409 selects intra prediction or inter predictionin accordance with information that is appended to the bitstream andindicates the prediction mode to be used. Note that predictioncontroller 1409 may continuously select intra prediction when it hasbeen decided in advance to decode the decoding target space using intraspace.

Hereinafter, variations of the present embodiment will be described. Inthe present embodiment, an example has been described in which rotationand translation is applied in units of spaces, but rotation andtranslation may also be applied in smaller units. For example,three-dimensional data encoding device 1300 may divide a space intosubspaces, and apply rotation and translation in units of subspaces. Inthis case, three-dimensional data encoding device 1300 generates RTinformation per subspace, and appends the generated RT information to aheader and the like of the bitstream. Three-dimensional data encodingdevice 1300 may apply rotation and translation in units of volumes,which is an encoding unit. In this case, three-dimensional data encodingdevice 1300 generates RT information in units of encoded volumes, andappends the generated RT information to a header and the like of thebitstream. The above may also be combined. In other words,three-dimensional data encoding device 1300 may apply rotation andtranslation in large units and subsequently apply rotation andtranslation in small units. For example, three-dimensional data encodingdevice 1300 may apply rotation and translation in units of spaces, andmay also apply different rotations and translations to each of aplurality of volumes included in the obtained spaces.

In the present embodiment, an example has been described in whichrotation and translation is applied to the reference space, but is notnecessarily limited thereto. For example, three-dimensional dataencoding device 1300 may apply a scaling process and change a size ofthe three-dimensional data. Three-dimensional data encoding device 1300may also apply one or two of the rotation, translation, and scaling.When applying the processes in multiple stages and different units asstated above, a type of the processes applied in each unit may differ.For example, rotation and translation may be applied in units of spaces,and translation may be applied in units of volumes.

Note that these variations are also applicable to three-dimensional datadecoding device 1400.

As stated above, three-dimensional data encoding device 1300 accordingto the present embodiment performs the following processes. FIG. 48 is aflowchart of the inter prediction process performed by three-dimensionaldata encoding device 1300.

Three-dimensional data encoding device 1300 generates predicted positioninformation (e.g. predicted volume) using position information onthree-dimensional points included in three-dimensional reference data(e.g. reference space) associated with a time different from a timeassociated with current three-dimensional data (e.g. encoding targetspace) (S1301). To be specific, three-dimensional data encoding device1300 generates the predicted position information by applying a rotationand translation process to the position information on thethree-dimensional points included in the three-dimensional referencedata.

Note that three-dimensional data encoding device 1300 may perform arotation and translation process using a first unit (e.g. spaces), andmay perform the generating of the predicted position information using asecond unit (e.g. volumes) that is smaller than the first unit. Forexample, three-dimensional data encoding device 1300 searches a volumeamong a plurality of volumes included in the rotated and translatedreference space, whose position information differs the least from theposition information of the encoding target volume included in theencoding target space. Note that three-dimensional data encoding device1300 may perform the rotation and translation process, and thegenerating of the predicted position information in the same unit.

Three-dimensional data encoding device 1300 may generate the predictedposition information by applying (i) a first rotation and translationprocess to the position information on the three-dimensional pointsincluded in the three-dimensional reference data, and (ii) a secondrotation and translation process to the position information on thethree-dimensional points obtained through the first rotation andtranslation process, the first rotation and translation process using afirst unit (e.g. spaces) and the second rotation and translation processusing a second unit (e.g. volumes) that is smaller than the first unit.

For example, as illustrated in FIG. 41, the position information on thethree-dimensional points and the predicted position information isrepresented using an octree structure. For example, the positioninformation on the three-dimensional points and the predicted positioninformation is expressed in a scan order that prioritizes a breadth overa depth in the octree structure. For example, the position informationon the three-dimensional points and the predicted position informationis expressed in a scan order that prioritizes a depth over a breadth inthe octree structure.

As illustrated in FIG. 46, three-dimensional data encoding device 1300encodes an RT flag that indicates whether to apply the rotation andtranslation process to the position information on the three-dimensionalpoints included in the three-dimensional reference data. In other words,three-dimensional data encoding device 1300 generates the encoded signal(encoded bitstream) including the RT flag. Three-dimensional dataencoding device 1300 encodes RT information that indicates contents ofthe rotation and translation process. In other words, three-dimensionaldata encoding device 1300 generates the encoded signal (encodedbitstream) including the RT information. Note that three-dimensionaldata encoding device 1300 may encode the RT information when the RT flagindicates to apply the rotation and translation process, and does notneed to encode the RT information when the RT flag indicates not toapply the rotation and translation process.

The three-dimensional data includes, for example, the positioninformation on the three-dimensional points and the attributeinformation (color information, etc.) of each three-dimensional point.Three-dimensional data encoding device 1300 generates predictedattribute information using the attribute information of thethree-dimensional points included in the three-dimensional referencedata (S1302).

Three-dimensional data encoding device 1300 next encodes the positioninformation on the three-dimensional points included in the currentthree-dimensional data, using the predicted position information. Forexample, as illustrated in FIG. 38, three-dimensional data encodingdevice 1300 calculates differential position information, thedifferential position information being a difference between thepredicted position information and the position information on thethree-dimensional points included in the current three-dimensional data(S1303).

Three-dimensional data encoding device 1300 encodes the attributeinformation of the three-dimensional points included in the currentthree-dimensional data, using the predicted attribute information. Forexample, three-dimensional data encoding device 1300 calculatesdifferential attribute information, the differential attributeinformation being a difference between the predicted attributeinformation and the attribute information on the three-dimensionalpoints included in the current three-dimensional data (S1304).Three-dimensional data encoding device 1300 next performs transformationand quantization on the calculated differential attribute information(S1305).

Lastly, three-dimensional data encoding device 1300 encodes (e.g.entropy encodes) the differential position information and the quantizeddifferential attribute information (S1036). In other words,three-dimensional data encoding device 1300 generates the encoded signal(encoded bitstream) including the differential position information andthe differential attribute information.

Note that when the attribute information is not included in thethree-dimensional data, three-dimensional data encoding device 1300 doesnot need to perform steps S1302, S1304, and S1305. Three-dimensionaldata encoding device 1300 may also perform only one of the encoding ofthe position information on the three-dimensional points and theencoding of the attribute information of the three-dimensional points.

An order of the processes shown in FIG. 49 is merely an example and isnot limited thereto. For example, since the processes with respect tothe position information (S1301 and S1303) and the processes withrespect to the attribute information (S1302, S1304, and S1305) areseparate from one another, they may be performed in an order of choice,and a portion thereof may also be performed in parallel.

With the above, three-dimensional data encoding device 1300 according tothe present embodiment generates predicted position information usingposition information on three-dimensional points included inthree-dimensional reference data associated with a time different from atime associated with current three-dimensional data; and encodesdifferential position information, which is a difference between thepredicted position information and the position information on thethree-dimensional points included in the current three-dimensional data.This makes it possible to improve encoding efficiency since it ispossible to reduce the amount of data of the encoded signal.

Three-dimensional data encoding device 1300 according to the presentembodiment generates predicted attribute information using attributeinformation on three-dimensional points included in three-dimensionalreference data; and encodes differential attribute information, which isa difference between the predicted attribute information and theattribute information on the three-dimensional points included in thecurrent three-dimensional data. This makes it possible to improveencoding efficiency since it is possible to reduce the amount of data ofthe encoded signal.

For example, three-dimensional data encoding device 1300 includes aprocessor and memory. The processor uses the memory to perform the aboveprocesses;

FIG. 48 is a flowchart of the inter prediction process performed bythree-dimensional data decoding device 1400.

Three-dimensional data decoding device 1400 decodes (e.g. entropydecodes) the differential position information and the differentialattribute information from the encoded signal (encoded bitstream)(S1401).

Three-dimensional data decoding device 1400 decodes, from the encodedsignal, an RT flag that indicates whether to apply the rotation andtranslation process to the position information on the three-dimensionalpoints included in the three-dimensional reference data.Three-dimensional data decoding device 1400 encodes RT information thatindicates contents of the rotation and translation process. Note thatthree-dimensional data decoding device 1400 may decode the RTinformation when the RT flag indicates to apply the rotation andtranslation process, and does not need to decode the RT information whenthe RT flag indicates not to apply the rotation and translation process.

Three-dimensional data decoding device 1400 next performs inversetransformation and inverse quantization on the decoded differentialattribute information (S1402).

Three-dimensional data decoding device 1400 next generates predictedposition information (e.g. predicted volume) using the positioninformation on the three-dimensional points included in thethree-dimensional reference data (e.g. reference space) associated witha time different from a time associated with the currentthree-dimensional data (e.g. decoding target space) (S1403). To bespecific, three-dimensional data decoding device 1400 generates thepredicted position information by applying a rotation and translationprocess to the position information on the three-dimensional pointsincluded in the three-dimensional reference data.

More specifically, when the RT flag indicates to apply the rotation andtranslation process, three-dimensional data decoding device 1400 appliesthe rotation and translation process on the position information on thethree-dimensional points included in the three-dimensional referencedata indicated in the RT information. In contrast, when the RT flagindicates not to apply the rotation and translation process,three-dimensional data decoding device 1400 does not apply the rotationand translation process on the position information on thethree-dimensional points included in the three-dimensional referencedata.

Note that three-dimensional data decoding device 1400 may perform therotation and translation process using a first unit (e.g. spaces), andmay perform the generating of the predicted position information using asecond unit (e.g. volumes) that is smaller than the first unit. Notethat three-dimensional data decoding device 1400 may perform therotation and translation process, and the generating of the predictedposition information in the same unit.

Three-dimensional data decoding device 1400 may generate the predictedposition information by applying (i) a first rotation and translationprocess to the position information on the three-dimensional pointsincluded in the three-dimensional reference data, and (ii) a secondrotation and translation process to the position information on thethree-dimensional points obtained through the first rotation andtranslation process, the first rotation and translation process using afirst unit (e.g. spaces) and the second rotation and translation processusing a second unit (e.g. volumes) that is smaller than the first unit.

For example, as illustrated in FIG. 41, the position information on thethree-dimensional points and the predicted position information isrepresented using an octree structure. For example, the positioninformation on the three-dimensional points and the predicted positioninformation is expressed in a scan order that prioritizes a breadth overa depth in the octree structure. For example, the position informationon the three-dimensional points and the predicted position informationis expressed in a scan order that prioritizes a depth over a breadth inthe octree structure.

Three-dimensional data decoding device 1400 generates predictedattribute information using the attribute information of thethree-dimensional points included in the three-dimensional referencedata (S1404).

Three-dimensional data decoding device 1400 next restores the positioninformation on the three-dimensional points included in the currentthree-dimensional data, by decoding encoded position informationincluded in an encoded signal, using the predicted position information.The encoded position information here is the differential positioninformation. Three-dimensional data decoding device 1400 restores theposition information on the three-dimensional points included in thecurrent three-dimensional data, by adding the differential positioninformation to the predicted position information (S1405).

Three-dimensional data decoding device 1400 restores the attributeinformation of the three-dimensional points included in the currentthree-dimensional data, by decoding encoded attribute informationincluded in an encoded signal, using the predicted attributeinformation. The encoded attribute information here is the differentialposition information. Three-dimensional data decoding device 1400restores the attribute information on the three-dimensional pointsincluded in the current three-dimensional data, by adding thedifferential attribute information to the predicted attributeinformation (S1406).

Note that when the attribute information is not included in thethree-dimensional data, three-dimensional data decoding device 1400 doesnot need to perform steps S1402, S1404, and S1406. Three-dimensionaldata decoding device 1400 may also perform only one of the decoding ofthe position information on the three-dimensional points and thedecoding of the attribute information of the three-dimensional points.

An order of the processes shown in FIG. 50 is merely an example and isnot limited thereto. For example, since the processes with respect tothe position information (S1403 and S1405) and the processes withrespect to the attribute information (S1402, S1404, and S1406) areseparate from one another, they may be performed in an order of choice,and a portion thereof may also be performed in parallel.

Embodiment 8

In the present embodiment, a representation means of three-dimensionalpoints (point cloud) in encoding of three-dimensional data will bedescribed;

FIG. 51 is a block diagram showing a structure of a distribution systemof three-dimensional data according to the present embodiment. Thedistribution system shown in FIG. 51 includes server 1501 and aplurality of clients 1502.

Server 1501 includes storage 1511 and controller 1512. Storage 1511stores encoded three-dimensional map 1513 that is encodedthree-dimensional data;

FIG. 52 is a diagram showing an example structure of a bitstream ofencoded three-dimensional map 1513. The three-dimensional map is dividedinto a plurality of submaps and each submap is encoded. Each submap isappended with a random-access (RA) header including subcoordinateinformation. The subcoordinate information is used for improvingencoding efficiency of the submap. This subcoordinate informationindicates subcoordinates of the submap. The subcoordinates arecoordinates of the submap having reference coordinates as reference.Note that the three-dimensional map including the plurality of submapsis referred to as an overall map. Coordinates that are a reference inthe overall map (e.g. origin) are referred to as the referencecoordinates. In other words, the subcoordinates are the coordinates ofthe submap in a coordinate system of the overall map. In other words,the subcoordinates indicate an offset between the coordinate system ofthe overall map and a coordinate system of the submap. Coordinates inthe coordinate system of the overall map having the referencecoordinates as reference are referred to as overall coordinates.Coordinates in the coordinate system of the submap having thesubcoordinates as reference are referred to as differential coordinates.

Client 1502 transmits a message to server 1501. This message includesposition information on client 1502. Controller 1512 included in server1501 obtains a bitstream of a submap located closest to client 1502,based on the position information included in the received message. Thebitstream of the submap includes the subcoordinate information and istransmitted to client 1502. Decoder 1521 included in client 1502 obtainsoverall coordinates of the submap having the reference coordinates asreference, using this subcoordinate information. Application 1522included in client 1502 executes an application relating to aself-location, using the obtained overall coordinates of the submap.

The submap indicates a partial area of the overall map. Thesubcoordinates are the coordinates in which the submap is located in areference coordinate space of the overall map. For example, in anoverall map called A, there is submap A called AA and submap B calledAB. When a vehicle wants to consult a map of AA, decoding begins fromsubmap A, and when the vehicle wants to consult a map of AB, decodingbegins from submap B. The submap here is a random-access point. To bespecific, A is Osaka Prefecture, AA is Osaka City, and AB is TakatsukiCity.

Each submap is transmitted along with the subcoordinate information tothe client. The subcoordinate information is included in headerinformation of each submap, a transmission packet, or the like.

The reference coordinates, which serve as a reference for thesubcoordinate information of each submap, may be appended to headerinformation of a space at a higher level than the submap, such as headerinformation of the overall map.

The submap may be formed by one space (SPC). The submap may also beformed by a plurality of SPCs.

The submap may include a Group of Spaces (GOS). The submap may be formedby a world. For example, in a case where there are a plurality ofobjects in the submap, the submap is formed by a plurality of SPCs whenassigning the plurality of objects to separate SPCs. The submap isformed by one SPC when assigning the plurality of objects to one SPC.

An advantageous effect on encoding efficiency when using thesubcoordinate information will be described next. FIG. 53 is a diagramfor describing this advantageous effect. For example, a high bit countis necessary in order to encode three-dimensional point A, which islocated far from the reference coordinates, shown in FIG. 53. A distancebetween the subcoordinates and three-dimensional point A is shorter thana distance between the reference coordinates and three-dimensional pointA. As such, it is possible to improve encoding efficiency by encodingcoordinates of three-dimensional point A having the subcoordinates asreference more than when encoding the coordinates of three-dimensionalpoint A having the reference coordinates as reference. The bitstream ofthe submap includes the subcoordinate information. By transmitting thebitstream of the submap and the reference coordinates to a decoding end(client), it is possible to restore the overall coordinates of thesubmap in the decoder end;

FIG. 54 is a flowchart of processes performed by server 1501, which is atransmission end of the submap.

Server 1501 first receives a message including position information onclient 1502 from client 1502 (S1501). Controller 1512 obtains an encodedbitstream of the submap based on the position information on the clientfrom storage 1511 (S1502). Server 1501 then transmits the encodedbitstream of the submap and the reference coordinates to client 1502(S1503);

FIG. 55 is a flowchart of processes performed by client 1502, which is areceiver end of the submap.

Client 1502 first receives the encoded bitstream of the submap and thereference coordinates transmitted from server 1501 (S1511). Client 1502next obtains the subcoordinate information of the submap by decoding theencoded bitstream (S1512). Client 1502 next restores the differentialcoordinates in the submap to the overall coordinates, using thereference coordinates and the subcoordinates (S1513).

An example syntax of information relating to the submap will bedescribed next. In the encoding of the submap, the three-dimensionaldata encoding device calculates the differential coordinates bysubtracting the subcoordinates from the coordinates of each point cloud(three-dimensional points). The three-dimensional data encoding devicethen encodes the differential coordinates into the bitstream as a valueof each point cloud. The encoding device encodes the subcoordinateinformation indicating the subcoordinates as the header information ofthe bitstream. This enables the three-dimensional data decoding deviceto obtain overall coordinates of each point cloud. For example, thethree-dimensional data encoding device is included in server 1501 andthe three-dimensional data decoding device is included in client 1502;

FIG. 56 is a diagram showing an example syntax of the submap. NumOfPointshown in FIG. 56 indicates a total number of point clouds included inthe submap. sub_coordinate_x, sub_coordinate_y, and sub_coordinate_z arethe subcoordinate information. sub_coordinate_x indicates anx-coordinate of the subcoordinates. sub_coordinate_y indicates ay-coordinate of the subcoordinates. sub_coordinate_z indicates az-coordinate of the subcoordinates.

diff_x[i], diff_y[i], and diff_z[i] are differential coordinates of ani-th point cloud in the submap. diff_x[i] is a differential valuebetween an x-coordinate of the i-th point cloud and the x-coordinate ofthe subcoordinates in the submap. diff_y[i] is a differential valuebetween a y-coordinate of the i-th point cloud and the y-coordinate ofthe subcoordinates in the submap. diff_z[i] is a differential valuebetween a z-coordinate of the i-th point cloud and the z-coordinate ofthe subcoordinates in the submap.

The three-dimensional data decoding device decodes point_cloud[i]_x,point_cloud[i]_y, and point_cloud[i]_z, which are overall coordinates ofthe i-th point cloud, using the expression below. point_cloud[i]_x is anx-coordinate of the overall coordinates of the i-th point cloud.point_cloud[i]_y is a y-coordinate of the overall coordinates of thei-th point cloud. point_cloud[i]_z is a z-coordinate of the overallcoordinates of the i-th point cloud.

point_cloud[i]_x=sub_coordinate_x+diff_x[i]

point_cloud[i]_y=sub_coordinate_y+diff_y[i]

point_cloud[i]_z=sub_coordinate_z+diff_z[i]

A switching process for applying octree encoding will be described next.The three-dimensional data encoding device selects, when encoding thesubmap, whether to encode each point cloud using an octreerepresentation (hereinafter, referred to as octree encoding) or toencode the differential values from the subcoordinates (hereinafter,referred to as non-octree encoding). FIG. 57 is a diagram schematicallyshowing this operation. For example, the three-dimensional data encodingdevice applies octree encoding to the submap, when the total number ofpoint clouds in the submap is at least a predetermined threshold. Thethree-dimensional data encoding device applies non-octree encoding tothe submap, when the total number of point clouds in the submap is lowerthan the predetermined threshold. This enables the three-dimensionaldata encoding device to improve encoding efficiency, since it ispossible to appropriately select whether to use octree encoding ornon-octree encoding, in accordance with a shape and density of objectsincluded in the submap.

The three-dimensional data encoding device appends, to a header and thelike of the submap, information indicating whether octree encoding ornon-octree encoding has been applied to the submap (hereinafter,referred to as octree encoding application information). This enablesthe three-dimensional data decoding device to identify whether thebitstream is obtained by octree encoding the submap or non-octreeencoding the submap.

The three-dimensional data encoding device may calculate encodingefficiency when applying octree encoding and encoding efficiency whenapplying non-octree encoding to the same point cloud, and apply anencoding method whose encoding efficiency is better to the submap;

FIG. 58 is a diagram showing an example syntax of the submap whenperforming this switching. coding_type shown in FIG. 58 is informationindicating the encoding type and is the above octree encodingapplication information. coding_type=00 indicates that octree encodinghas been applied. coding_type=01 indicates that non-octree encoding hasbeen applied. coding_type=10 or 11 indicates that an encoding method andthe like other than the above encoding methods has been applied.

When the encoding type is non-octree encoding (non_octree), the submapincludes NumOfPoint and the subcoordinate information (sub_coordinate_x,sub_coordinate_y, and sub_coordinate_z).

When the encoding type is octree encoding (octree), the submap includesoctree_info. octree_info is information necessary to the octree encodingand includes, for example, depth information.

When the encoding type is non-octree encoding (non_octree), the submapincludes the differential coordinates (diff_x[i], diff_y[i], anddiff_z[i]).

When the encoding type is octree encoding (octree), the submap includesoctree_data, which is encoded data relating to the octree encoding.

Note that an example has been described here in which an xyz coordinatesystem is used as the coordinate system of the point cloud, but a polarcoordinate system may also be used;

FIG. 59 is a flowchart of a three-dimensional data encoding processperformed by the three-dimensional data encoding device.Three-dimensional data encoding device first calculates a total numberof point clouds in a current submap, which is the submap to be processed(S1521). The three-dimensional data encoding device next determineswhether when the calculated total number of point clouds is at least apredetermined threshold (S1522).

When the total number of point clouds is at least the predeterminedthreshold (YES in S1522), the three-dimensional data encoding deviceapplies octree encoding to the current submap (S1523). Thethree-dimensional data encoding device appends, to a header of thebitstream, octree encoding application information indicating thatoctree encoding has been applied to the current submap (S1525).

In contrast, when the total number of point clouds is lower than thepredetermined threshold (NO in S1522), the three-dimensional dataencoding device applies non-octree encoding to the current submap(S1524). The three-dimensional data encoding device appends, to theheader of the bitstream, octree encoding application informationindicating that non-octree encoding has been applied to the currentsubmap (S1525);

FIG. 60 is a flowchart of a three-dimensional data decoding processperformed by the three-dimensional data decoding device. Thethree-dimensional data decoding device first decodes the octree encodingapplication information from the header of the bitstream (S1531). Thethree-dimensional data decoding device next determines whether theencoding type applied to the current submap is octree encoding, based onthe decoded octree encoding application information (S1532).

When the octree encoding application information indicates that theencoding type is octree encoding (YES in S1532), the three-dimensionaldata decoding device decodes the current submap through octree decoding(S1533). In contrast, when the octree encoding application informationindicates that the encoding type is non-octree encoding (NO in S1532),the three-dimensional data decoding device decodes the current submapthrough non-octree decoding (S1534).

Hereinafter, variations of the present embodiment will be described.FIG. 61 to FIG. 63 are diagrams schematically showing operations ofvariations of the switching process of the encoding type.

As illustrated in FIG. 61, the three-dimensional data encoding devicemay select whether to apply octree encoding or non-octree encoding perspace. In this case, the three-dimensional data encoding device appendsthe octree encoding application information to a header of the space.This enables the three-dimensional data decoding device to determinewhether octree encoding has been applied per space. In this case, thethree-dimensional data encoding device sets subcoordinates per space,and encodes a differential value, which is a value of the subcoordinatessubtracted from coordinates of each point cloud in the space.

This enables the three-dimensional data encoding device to improveencoding efficiency, since it is possible to appropriately selectwhether to apply octree encoding, in accordance with a shape of objectsor the total number of point clouds in the space.

As illustrated in FIG. 62, the three-dimensional data encoding devicemay select whether to apply octree encoding or non-octree encoding pervolume. In this case, the three-dimensional data encoding device appendsthe octree encoding application information to a header of the volume.This enables the three-dimensional data decoding device to determinewhether octree encoding has been applied per volume. In this case, thethree-dimensional data encoding device sets subcoordinates per volume,and encodes a differential value, which is a value of the subcoordinatessubtracted from coordinates of each point cloud in the volume.

This enables the three-dimensional data encoding device to improveencoding efficiency, since it is possible to appropriately selectwhether to apply octree encoding, in accordance with a shape of objectsor the total number of point clouds in the volume.

In the above description, an example has been shown in which thedifference, which is the subcoordinates of each point cloud subtractedfrom the coordinates of each point cloud, is encoded as the non-octreeencoding, but is not limited thereto, and any other type of encodingmethod other than the octree encoding may be used. For example, asillustrated in FIG. 63, the three-dimensional data encoding device maynot only encode the difference from the subcoordinates as the non-octreeencoding, but also use a method in which a value of the point cloud inthe submap, the space, or the volume itself is encoded (hereinafter,referred to as original coordinate encoding).

In this case, the three-dimensional data encoding device stores, in theheader, information indicating that original coordinate encoding hasbeen applied to a current space (submap, space, or volume). This enablesthe three-dimensional data decoding device to determine whether originalcoordinate encoding has been applied to the current space.

When applying original coordinate encoding, the three-dimensional dataencoding device may perform the encoding without applying quantizationand arithmetic encoding to original coordinates. The three-dimensionaldata encoding device may encode the original coordinates using apredetermined fixed bit length. This enables three-dimensional dataencoding device to generate a stream with a fixed bit length at acertain time.

In the above description, an example has been shown in which thedifference, which is the subcoordinates of each point cloud subtractedfrom the coordinates of each point cloud, is encoded as the non-octreeencoding, but is not limited thereto.

For example, the three-dimensional data encoding device may sequentiallyencode a differential value between the coordinates of each point cloud.FIG. 64 is a diagram for describing an operation in this case. Forexample, in the example shown in FIG. 64, the three-dimensional dataencoding device encodes a differential value between coordinates ofpoint cloud PA and predicted coordinates, using the subcoordinates asthe predicted coordinates, when encoding point cloud PA. Thethree-dimensional data encoding device encodes a differential valuebetween point cloud PB and predicted coordinates, using the coordinatesof point cloud PA as the predicted coordinates, when encoding pointcloud PB. The three-dimensional data encoding device encodes adifferential value between point cloud PC and predicted coordinates,using the coordinates of point cloud PB as the predicted coordinates,when encoding point cloud PC. In this manner, the three-dimensional dataencoding device may set a scan order to a plurality of point clouds, andencode a differential value between coordinates of a current point cloudto be processed and coordinates of a point cloud immediately before thecurrent point cloud in the scan order.

In the above description, the subcoordinates are coordinates in thelower left front corner of the submap, but a location of thesubcoordinates is not limited thereto. FIG. 65 to FIG. 67 are diagramsshowing other examples of the location of the subcoordinates. Thelocation of the subcoordinates may be set to any coordinates in thecurrent space (submap, space, or volume). In other words, thesubcoordinates may be, as stated above, coordinates in the lower leftfront corner of the current space. As illustrated in FIG. 65, thesubcoordinates may be coordinates in a center of the current space. Asillustrated in FIG. 66, the subcoordinates may be coordinates in anupper right rear corner of the current space. The subcoordinates are notlimited to being coordinates in the lower left front corner or the upperright rear corner of the current space, but may also be coordinates inany corner of the current space.

The location of the subcoordinates may be the same as coordinates of acertain point cloud in the current space (submap, space, or volume). Forexample, in the example shown in FIG. 67, the coordinates of thesubcoordinates coincide with coordinates of point cloud PD.

In the present embodiment, an example has been shown that switchesbetween applying octree encoding or non-octree encoding, but is notnecessarily limited thereto. For example, the three-dimensional dataencoding device may switch between applying a tree structure other thanan octree or a non-tree structure other than the tree-structure. Forexample, the other tree structure is a k-d tree in which splitting isperformed using perpendicular planes on one coordinate axis. Note thatany other method may be used as the other tree structure.

In the present embodiment, an example has been shown in which coordinateinformation included in a point cloud is encoded, but is not necessarilylimited thereto. The three-dimensional data encoding device may encode,for example, color information, a three-dimensional feature quantity, ora feature quantity of visible light using the same method as for thecoordinate information. For example, the three-dimensional data encodingdevice may set an average value of the color information included ineach point cloud in the submap to subcolor information, and encode adifference between the color information and the subcolor information ofeach point cloud.

In the present embodiment, an example has been shown in which anencoding method (octree encoding or non-octree encoding) with goodencoding efficiency is selected in accordance with a total number ofpoint clouds and the like, but is not necessarily limited thereto. Forexample, the three-dimensional data encoding device, which is a serverend, may store a bitstream of a point cloud encoded through octreeencoding, a bitstream of a point cloud encoded through non-octreeencoding, and a bitstream of a point cloud encoded through both methods,and switch the bitstream to be transmitted to the three-dimensional datadecoding device, in accordance with a transmission environment or aprocessing power of the three-dimensional data decoding device;

FIG. 68 is a diagram showing an example syntax of a volume when applyingoctree encoding. The syntax shown in FIG. 68 is basically the same asthe syntax shown in FIG. 58, but differs in that each piece ofinformation is information in units of volumes. To be specific,NumOfPoint indicates a total number of point clouds included in thevolume. sub_coordinate_x, sub_coordinate_y, and sub_coordinate_z are thesubcoordinate information of the volume.

diff_x[i], diff_y[i], and diff_z[i] are differential coordinates of ani-th point cloud in the volume. diff_x[i] is a differential valuebetween an x-coordinate of the i-th point cloud and the x-coordinate ofthe subcoordinates in the volume. diff_y[i] is a differential valuebetween a y-coordinate of the i-th point cloud and the y-coordinate ofthe subcoordinates in the volume. diff_z[i] is a differential valuebetween a z-coordinate of the i-th point cloud and the z-coordinate ofthe subcoordinates in the volume.

Note that when it is possible to calculate a relative position of thevolume in the space, the three-dimensional data encoding device does notneed to include the subcoordinate information in a header of the volume.In other words, the three-dimensional data encoding device may calculatethe relative position of the volume in the space without including thesubcoordinate information in the header, and use the calculated positionas the subcoordinates of each volume.

As stated above, the three-dimensional data encoding device according tothe present embodiment determines whether to encode, using an octreestructure, a current space unit among a plurality of space units (e.g.submaps, spaces, or volumes) included in three-dimensional data (e.g.S1522 in FIG. 59). For example, the three-dimensional data encodingdevice determines that the current space unit is to be encoded using theoctree structure, when a total number of the three-dimensional pointsincluded in the current space unit is higher than a predeterminedthreshold. The three-dimensional data encoding device determines thatthe current space unit is not to be encoded using the octree structure,when the total number of the three-dimensional points included in thecurrent space unit is lower than or equal to the predeterminedthreshold.

When it is determined that the current space unit is to be encoded usingthe octree structure (YES in S1522), the three-dimensional data encodingdevice encodes the current space unit using the octree structure(S1523). When it is determined that the current space unit is not to beencoded using the octree structure (NO in S1522), the three-dimensionaldata encoding device encodes the current space unit using a differentmethod that is not the octree structure (S1524). For example, in thedifferent method, the three-dimensional data encoding device encodescoordinates of three-dimensional points included in the current spaceunit. To be specific, in the different method, the three-dimensionaldata encoding device encodes a difference between reference coordinatesof the current space unit and the coordinates of the three-dimensionalpoints included in the current space unit.

The three-dimensional data encoding device next appends, to a bitstream,information that indicates whether the current space unit has beenencoded using the octree structure (S1525).

This enables the three-dimensional data encoding device to improveencoding efficiency since it is possible to reduce the amount of data ofthe encoded signal.

For example, the three-dimensional data encoding device includes aprocessor and memory, the processor using the memory to perform theabove processes.

The three-dimensional data decoding device according to the presentembodiment decodes, from a bitstream, information that indicates whetherto decode, using an octree structure, a current space unit among aplurality of space units (e.g. submaps, spaces, or volumes) included inthree-dimensional data (e.g. S1531 in FIG. 60). When the informationindicates that the current space unit is to be decoded using the octreestructure (YES in S1532), the three-dimensional data decoding devicedecodes the current space unit using the octree structure (S1533).

When the information indicates not to decode the current space unitusing the octree structure (NO in S1532), the three-dimensional datadecoding device decodes the current space unit using a different methodthat is not the octree structure (S1534). For example, in the differentmethod, the three-dimensional data decoding device decodes coordinatesof three-dimensional points included in the current space unit. To bespecific, in the different method, the three-dimensional data decodingdevice decodes a difference between reference coordinates of the currentspace unit and the coordinates of the three-dimensional points includedin the current space unit.

This enables the three-dimensional data decoding device to improveencoding efficiency since it is possible to reduce the amount of data ofthe encoded signal.

For example, three-dimensional data decoding device includes a processorand memory. The processor uses the memory to perform the aboveprocesses.

Embodiment 9

In the present embodiment, a method for encoding a tree structure suchas an octree structure will be described.

It is possible to improve efficiency by identifying an important areaand preferentially decoding three-dimensional data of the importantarea;

FIG. 69 is a diagram showing an example of an important area in athree-dimensional map. The important area includes, for example, atleast a fixed number of three-dimensional points, amongthree-dimensional points in the three-dimensional map, having a highfeature quantity. The important area may also include, for example, afixed number of three-dimensional points necessary when, for example, avehicle-mounted client performs self-location estimation. Alternatively,the important area may also be a face in a three-dimensional model of aperson. Such an important area can be defined per application type, andmay be switched in accordance therewith.

In the present embodiment, occupancy encoding and location encoding areused as a method for representing an octree structure and the like. Abit sequence obtained through occupancy encoding is referred to asoccupancy code. A bit sequence obtained through location encoding isreferred to as location code;

FIG. 70 is a diagram showing an example of an occupancy code. FIG. 70shows an example of the occupancy code of a quadtree structure. In FIG.70, occupancy code is assigned to each node. Each piece of occupancycode indicates whether a three-dimensional point is included in a childnode or a leaf of a node. In the case of a quadtree, for example,information, which indicates whether four child nodes or leaves includedin each node include three-dimensional points, is expressed with a 4-bitoccupancy code. In the case of an octree, information, which indicateswhether eight child nodes or leaves included in each node includethree-dimensional points, is expressed with an 8-bit occupancy code.Note that an example of a quadtree structure is described here in orderto simplify the description, but the same is applicable to an octreestructure. As illustrated in FIG. 70, for example, the occupancy code isa bit sequence in which the nodes and leaves have been scannedbreadth-first, as described in FIG. 40, etc. In the occupancy code,since a plurality of pieces of three-dimensional point information aredecoded in a fixed order, it is not possible to preferentially decode apiece of three-dimensional point information of choice. Note that theoccupancy code may also be a bit sequence in which the nodes and leaveshave been scanned depth-first, as described in FIG. 40, etc.

Hereinafter, location encoding will be described. It is possible todirectly decode important portions in the octree structure by using thelocation code. It is also possible to efficiently encode the importantthree-dimensional points in deeper levels;

FIG. 71 is a diagram for describing location encoding and shows anexample of a quadtree structure. In the example shown in FIG. 71,three-dimensional points A-I are represented with a quadtree structure.Three-dimensional points A and C are important three-dimensional pointsincluded in the important area;

FIG. 72 is a diagram showing occupancy codes and location codesexpressing important three-dimensional points A and C in the quadtreestructure shown in FIG. 71.

In the location encoding, an index of each node present on a path upuntil a leaf to which a current three-dimensional point belongs that isan encoding target three-dimensional point, and an index of each leaf inthe tree structure are encoded. The index here is a numerical valueassigned to each node and each leaf. In other words, the index is anidentifier for identifying child nodes of a current node. In the case ofthe quadtree as shown in FIG. 71, indexes between 0 and 3 are shown.

In the quadtree structure shown in FIG. 71, for example, leaf A isrepresented as 0→2→1→0→1→2→1 when leaf A is the currentthree-dimensional point. Since a maximum value of each index in the caseof FIG. 71 is 4 (representable as 2-bit value), a bit count necessaryfor the location code of leaf A is 7×2 bits=14 bits. Similarly, a bitcount necessary when leaf C is the encoding target is 14 bits. Note thatin the case of an octree, it is possible to calculate a bit countnecessary for 3 bits×leaf depth, since the maximum value of each indexis 8 (representable as 3-bit value). Note that the three-dimensionaldata encoding device may reduce a data amount through entropy encodingafter binarizing each index.

As illustrated in FIG. 72, in the occupancy code, it is necessary todecode all nodes of upper levels of leaves A and C in order to decodeleaves A and C. On the other hand, it is possible to only decode data ofleaves A and C in the location code. As illustrated in FIG. 72, thismakes it possible to reduce bit count more than with the occupancy codeby using the location code.

As illustrated in FIG. 72, it is possible to further reduce a codeamount by performing dictionary compression such as LZ77 on a portion orall of the location code.

An example in which location encoding is applied to three-dimensionalpoints (point cloud) obtained through LiDAR will be described next. FIG.73 is a diagram showing the example of the three-dimensional pointsobtained through LiDAR. The three-dimensional points obtained throughLiDAR are sparsely disposed. In other words, when expressing thesethree-dimensional points with an occupancy code, a number of zero valuesis high. High three-dimensional precision is required for thesethree-dimensional points. In other words, the hierarchy of the octreestructure becomes deeper;

FIG. 74 is a diagram showing an example of such a sparse and deep octreestructure. An occupancy code of the octree structure shown in FIG. 74 isa 136-bit value (=8 bits×17 nodes). Since the octree structure has adepth of 6 and six three-dimensional points, the location code is 3bits×6×6=108 bits. In other words, the location code is capable ofreducing 20% of a code amount of the occupancy code. In this manner, itis possible to reduce the code amount by applying location encoding tothe sparse and deep octree structure.

Hereinafter, the code amounts of the occupancy code and the locationcode will be described. When the octree structure has a depth of 10, amaximum number of three-dimensional points is 8¹⁰=1,073,741,824. Bitcount L of the occupancy code of the octree structure is expressedbelow.

L ₀=8+8²+ . . . +8¹⁰=127,133,512 bits

As such, a bit count of one three-dimensional point is 1.143 bits. Notethat in the occupancy code, this bit count does not change even if thetotal number of three-dimensional points included in the octreestructure changes.

On the other hand, in the location code, a bit count of onethree-dimensional point is directly influenced by the depth of theoctree structure. To be specific, a bit count of the location code ofone three-dimensional point is 3 bits×depth of 10=30 bits.

As such, bit count L₁ of the location code of the octree structure isexpressed below.

L ₁=30×N

N here is the total number of three-dimensional points included in theoctree structure.

As such, in the case of N<L₀/30=40,904,450.4, i.e., when the totalnumber of three-dimensional points is lower than 40,904,450, the codeamount of the location code is smaller than the code amount of theoccupancy code (L₁<L₀).

In this manner, the code amount of the location code is lower than thecode amount of the occupancy code in the case of a low number ofthree-dimensional points, and the code amount of the location code ishigher than the code amount of the occupancy code in the case of a highnumber of three-dimensional points.

As such, the three-dimensional data encoding device may switch betweenusing location encoding or occupancy encoding in accordance with thetotal number of inputted three-dimensional points. In this case, thethree-dimensional data encoding device may append, to header informationand the like of the bitstream, information indicating whether thelocation encoding or the occupancy encoding has been performed.

Hereinafter, hybrid encoding, which is a combination of the locationencoding and the occupancy encoding, will be described. When encoding adense important area, hybrid encoding, which is a combination of thelocation encoding and the occupancy encoding, is effective. FIG. 75 is adiagram showing this example. In the example shown in FIG. 75, theimportant three-dimensional points are disposed densely. In this case,the three-dimensional data encoding device performs location encoding onthe upper levels at a shallow depth and uses occupancy encoding for thelower levels. To be specific, location encoding is used up until adeepest common node and occupancy encoding is used from the deepestcommon node up until the deepest level. The deepest common node here isthe deepest node among nodes that are the common ancestors of theplurality of important three-dimensional points.

Hybrid encoding that prioritizes compression efficiency will bedescribed next. The three-dimensional data encoding device may switchbetween location encoding or occupancy encoding in accordance with apredetermined rule during encoding of the octree;

FIG. 76 is a diagram showing an example of this rule. Thethree-dimensional data encoding device first checks a percentage ofnodes including three-dimensional points at each level (depth). When thepercentage is higher than a predetermined threshold value, thethree-dimensional data encoding device occupancy encodes several nodesof upper levels of the current level. For example, the three-dimensionaldata encoding device applies occupancy encoding from the current levelto levels up until the deepest common node.

For example, in the example of FIG. 76, the percentage of nodesincluding three-dimensional points in a third level is higher than thepredetermined threshold value. As such, the three-dimensional dataencoding device applies occupancy encoding from the third level up untilthe second level including the deepest common node, and applies locationencoding to the other levels, i.e., the first level and the fourthlevel.

A method for calculating the above threshold value will be described.One level of the octree structure includes one root node and eight childnodes. As such, in the occupancy encoding, 8 bits are necessary forencoding one level of the octree structure. On the other hand, in thelocation encoding, 3 bits are necessary per child node including athree-dimensional point. As such, when a total number of nodes includingthree-dimensional points is higher than 2, occupancy encoding is moreeffective than location encoding. In other words, in this case, thethreshold value is 2.

Hereinafter, an example structure of a bitstream generated through theabove-mentioned location encoding, occupancy encoding, or hybridencoding will be described;

FIG. 77 is a diagram showing an example of a bitstream generated throughlocation encoding. As illustrated in FIG. 77, the bitstream generatedthrough location encoding includes a header and pieces of location code.Each piece of location code corresponds to one three-dimensional point.

This structure enables the three-dimensional data decoding device toindividually decode a plurality of three-dimensional points will highprecision. Note that FIG. 77 shows an example of a bitstream in the caseof a quadtree structure. In the case of an octree structure, each indexcan take a value between 0 and 7.

The three-dimensional data encoding device may entropy encode an indexsequence expressing one three-dimensional point after binarizing theindex sequence. For example, when the index sequence is 0121, thethree-dimensional data encoding device may binarize 0121 into 00011001and perform arithmetic encoding on this bit sequence;

FIG. 78 is a diagram showing an example of a bitstream generated throughhybrid encoding when the bitstream includes important three-dimensionalpoints. As illustrated in FIG. 78, location code of upper levels,occupancy code of important three-dimensional points of lower levels,and occupancy code of non-important three-dimensional points of lowerlevels are disposed in this order. Note that a location code lengthshown in FIG. 78 expresses a code amount of subsequent location code. Anoccupancy code amount expresses a code amount of subsequent occupancycode.

This structure enables the three-dimensional data decoding device toselect a decoding plan in accordance with the type of application.

Encoded data of the important three-dimensional points is stored arounda head of the bitstream, and encoded data of the non-importantthree-dimensional points not included in the important area is storedbehind the encoded data of the important three-dimensional points;

FIG. 79 is a diagram showing a tree structure expressed with theoccupancy code of the important three-dimensional points shown in FIG.78. FIG. 80 is a diagram showing a tree structure expressed with theoccupancy code of the non-important three-dimensional points shown inFIG. 78. As illustrated in FIG. 79, information relating to thenon-important three-dimensional points is excluded in the occupancy codeof the important three-dimensional points. To be specific, since node 0and node 3 at a depth of 5 do not include important three-dimensionalpoints, value 0 is assigned indicating that node 0 and node 3 do notinclude three-dimensional points.

On the other hand, as illustrated in FIG. 80, information relating tothe important three-dimensional points is excluded in the occupancy codeof the non-important three-dimensional points. To be specific, sincenode 1 at a depth of 5 does not include non-important three-dimensionalpoints, value 0 is assigned indicating that node 1 does not include athree-dimensional point.

In this manner, the three-dimensional data encoding device divides theoriginal tree structure into a first tree structure including theimportant three-dimensional points and a second tree structure includingthe non-important three-dimensional points, and separately occupancyencodes the first tree structure and the second tree structure. Thisenables the three-dimensional data decoding device to preferentiallydecode the important three-dimensional points.

An example structure of a bitstream generated through hybrid encodingemphasizing efficiency will be described next. FIG. 81 is a diagramshowing the example structure of the bitstream generated through hybridencoding emphasizing efficiency. As illustrated in FIG. 81, a subtreeroot location, occupancy code amount, and occupancy code are disposedper subtree in this order. The subtree root location shown in FIG. 81 isthe location code of the root of the subtree.

In the above structure, the following holds true when only one oflocation encoding or occupancy encoding is applied to the octreestructure.

When the length of the location code of the root of the subtree isidentical to the depth of the octree structure, the subtree does notinclude any child nodes. In other words, location encoding is applied tothe entire tree structure.

When the root of the subtree is identical to the root of the octreestructure, occupancy encoding is applied to the entire tree structure.

For example, the three-dimensional data decoding device is capable ofdiscerning whether the bitstream includes location code or occupancycode, based on the above rule.

The bitstream may include encoding mode information indicating which oflocation encoding, occupancy encoding, and hybrid encoding is used. FIG.82 is a diagram showing an example of a bitstream in this case. Asillustrated in FIG. 82, for example, 2-bit encoding mode informationindicating the encoding mode is appended to the bitstream.

(1) “THREE-DIMENSIONAL POINT COUNT” in the location encoding expresses atotal number of subsequent three-dimensional points. (2) “OCCUPANCY CODEAMOUNT” in the occupancy encoding expresses a code amount of subsequentoccupancy code. (3) “IMPORTANT SUBTREE COUNT” in the hybrid encoding(important three-dimensional points) expresses a total number ofsubtrees including important three-dimensional points. (4) “OCCUPANCYSUBTREE COUNT” in the hybrid encoding (emphasis on efficiency) expressesa total number of occupancy encoded subtrees.

An example syntax used for switching between applying occupancy encodingor location encoding will be described next. FIG. 83 is a diagramshowing this example syntax.

isleaf shown in FIG. 83 is a flag indicating whether the current node isa leaf. isleaf=1 indicates that the current node is a leaf, and isleaf=0indicates that the current node is not a leaf.

When the current node is a leaf, point_flag is appended to thebitstream. point_flag is a flag indicating whether the current node(lea) includes a three-dimensional point. point_flag=1 indicates thatthe current node includes a three-dimensional point, and point_flag=0indicates that the current node does not include a three-dimensionalpoint.

When the current node is not a leaf coding_type is appended to thebitstream. coding_type is encoding type information indicating whichencoding type has been applied. coding_type=00 indicates that locationencoding has been applied, coding_type=01 indicates that occupancyencoding has been applied, and coding_type=10 or 11 indicates thatanother encoding method has been applied.

When the encoding type is location encoding, numPoint, num_idx[i], andidx[i][j] are appended to the bitstream.

numPoint indicates a total number of three-dimensional points on whichto perform location encoding. num_idx[i] indicates a total number(depth) of indexes from the current node up to three-dimensional pointi. When the three-dimensional points on which location encoding is to beperformed are all at the same depth, each num_idx[i] has the same value.As such, num_idx may be defined as a common value before the forstatement (for (i=0;i<numPoint;i++){) shown in FIG. 83.

idx[i][j] indicates a value of a j-th index among indexes from thecurrent node up to three-dimensional point i. In the case of an octree,a bit count of idx[i][j] is 3 bits.

Note that, as stated above, the index is an identifier for theidentifying child nodes of the current node. In the case of an octree,idx[i][j] indicates a value between 0 and 7. In the case of an octree,there are eight child nodes which respectively correspond to eightsubblocks obtained by spatially dividing a current block correspondingto the current node into eight. As such, idx[i][j] may be informationindicating a three-dimensional position of the subblock corresponding toa child node. For example, idx[i][j] may be 3-bit information in totalincludes three pieces of 1-bit information each indicating a position ofeach of x, y, and z of the subblock.

When the encoding type is occupancy encoding, occupancy_code is appendedto the bitstream. occupancy_code is the occupancy code of the currentnode. In the case of an octree, occupancy_code is an 8-bit bit sequencesuch as bit sequence “00101000”.

When a value of an (i+1)-th bit of occupancy_code is 1, processing ofthe child node begins. In other words, the child node is set as the nextcurrent node, and a bit sequence is recursively generated.

In the present embodiment, an example is shown in which ends of theoctree are expressed by appending leaf information (isleaf, point_flag)to the bitstream, but the present embodiment is not necessarily limitedthereto. For example, the three-dimensional data encoding device mayappend, to a header portion of a start-node (root), a maximum depth fromthe start-node of the occupancy code up to ends (leaves) includingthree-dimensional points. The three-dimensional data encoding device mayrecursively convert information on the child nodes while increasing thedepth from the start-node, and may determine as to having arrived at theleaves when the depth becomes the maximum depth. The three-dimensionaldata encoding device may also append information indicating the maximumdepth to the first node where the coding type has become occupancyencoding, and may also append this information to the start-node (root)of the octree.

As stated above, the three-dimensional data encoding device may append,to the bitstream, information for switching between occupancy encodingand location encoding as header information of each node.

The three-dimensional data encoding device may entropy encodecoding_type, numPoint, num_idx, idx, and occupancy_code of each nodegenerated using the above method. For example, the three-dimensionaldata encoding device arithmetically encodes each value after binarizingeach value.

In the above syntax, an example is shown of when a depth-first bitsequence of the octree structure is used as the occupancy code, but thepresent embodiment is not necessarily limited thereto. Thethree-dimensional data encoding device may use a breadth-first bitsequence of the octree structure as the occupancy code. Thethree-dimensional data encoding device may append, to the bitstream,information for switching between occupancy encoding and locationencoding as header information of each node, also when using abreadth-first bit sequence.

In the present embodiment, an example has been shown of an octreestructure, but the present embodiment is not necessarily limitedthereto, and the above method may be applied to an N-ary (N is aninteger of 2 or higher) structure such as a quadtree or a hextree, oranother tree structure.

Hereinafter, a flow example of an encoding process for switching betweenapplying occupancy encoding or location encoding will be described. FIG.84 is a flowchart of the encoding process according to the presentembodiment.

The three-dimensional data encoding device first represents a pluralityof three-dimensional points included in three-dimensional data using anoctree structure (S1601). The three-dimensional data encoding devicenext sets a root in the octree structure as a current node (S1602). Thethree-dimensional data encoding device next generates a bit sequence ofthe octree structure by performing a node encoding process on thecurrent node (S1603). The three-dimensional data encoding device nextgenerates a bit sequence by entropy encoding the generated bit sequence(S1604);

FIG. 85 is a flowchart of the node encoding process (S1603). Thethree-dimensional data encoding device first determines whether thecurrent node is a leaf (S1611). When the current node is not a leaf (NOin S1611), the three-dimensional data encoding device sets a leaf flag(isleaf to 0, and appends the leaf flag to the bit sequence (S1612).

The three-dimensional data encoding device next determines whether atotal number of child nodes including three-dimensional points is higherthan a predetermined threshold value (S1613). Note thatthree-dimensional data encoding device may append this threshold valueto the bit sequence.

When the total number of child nodes including three-dimensional pointsis higher than the predetermined threshold value (YES in S1613), thethree-dimensional data encoding device sets the encoding type(coding_type) to occupancy encoding, and appends the encoding type tothe bit sequence (S1614).

The three-dimensional data encoding device next configures occupancyencoding information, and appends the occupancy encoding information tothe bit sequence. To be specific, the three-dimensional data encodingdevice generates an occupancy code for the current node, and appends theoccupancy code to the bit sequence (S1615).

The three-dimensional data encoding device next sets the next currentnode based on the occupancy code (S1616). To be specific, thethree-dimensional data encoding device sets the next current node froman unprocessed child node whose occupancy code is “1”.

The three-dimensional data encoding device performs the node encodingprocess on the newly-set current node (S1617). In other words, theprocess shown in FIG. 85 is performed on the newly-set current node.

When all child nodes have not been processed yet (NO in S1618), theprocesses from step S1616 are performed again. On the other hand, whenall of the child nodes have been processed (YES in S1618), thethree-dimensional data encoding device ends the node encoding process.

In step S1613, when the total number of child nodes includingthree-dimensional points is lower than or equal to the predeterminedthreshold value (NO in S1613), the three-dimensional data encodingdevice sets the encoding type to location encoding, and appends theencoding type to the bit sequence (S1619).

The three-dimensional data encoding device next configures locationencoding information, and appends the location encoding information tothe bit sequence. To be specific, the three-dimensional data encodingdevice next generates a location code, and appends the location code tothe bit sequence (S1620). The location code includes numPoint, num_idx,and idx.

In step S1611, when the current node is a leaf (YES in S1611), thethree-dimensional data encoding device sets the leaf flag to I, andappends the leaf flag to the bit sequence (S1621). The three-dimensionaldata encoding device configures a point flag (point_flag) that isinformation indicating whether the leaf includes a three-dimensionalpoint, and appends the point flag to the bit sequence (S1622).

A flow example of a decoding process for switching between applyingoccupancy encoding or location encoding will be described next. FIG. 85is a flowchart of the decoding process according to the presentembodiment.

The three-dimensional data encoding device generates a bit sequence byentropy decoding the bitstream (S1631). The three-dimensional datadecoding device next restores the octree structure by performing a nodedecoding process on the obtained bit sequence (S1632). Thethree-dimensional data decoding device next generates thethree-dimensional points from the restores octree structure (S1633);

FIG. 87 is a flowchart of the node decoding process (S1632). Thethree-dimensional data decoding device first obtains (decodes) the leafflag (isleaf) from the bit sequence (S1641). The three-dimensional datadecoding device next determines whether the current node is a leaf basedon the leaf flag (S1642).

When the current node is not a leaf (NO in S1642), the three-dimensionaldata decoding device obtains the encoding type (coding_type) from thebit sequence (S1643). The three-dimensional data decoding devicedetermines whether the encoding type is occupancy encoding (S1644).

When the encoding type is occupancy encoding (YES in S1644), thethree-dimensional data decoding device obtains the occupancy encodinginformation from the bit sequence. To be specific, the three-dimensionaldata decoding device obtains the occupancy code from the bit sequence(S1645).

The three-dimensional data decoding device next sets the next currentnode based on the occupancy code (S1646). To be specific, thethree-dimensional data decoding device sets the next current node froman unprocessed child node whose occupancy code is “1”.

The three-dimensional data decoding device next performs the nodedecoding process on the newly-set current node (S1647). In other words,the process shown in FIG. 87 is performed on the newly-set current node.

When all child nodes have not been processed yet (NO in S1648), theprocesses from step S1646 are performed again. On the other hand, whenall of the child nodes have been processed (YES in S1648), thethree-dimensional data decoding device ends the node decoding process.

In step 1644, when the encoding type is location encoding (NO in S1644),the three-dimensional data decoding device obtains the location encodinginformation from the bit sequence. To be specific, the three-dimensionaldata decoding device obtains the location code from the bit sequence(S1649). The location code includes numPoint, num_idx, and idx.

In step S1642, when the current node is a leaf (YES in S1642), thethree-dimensional data decoding device obtains, from the bit sequence,the point flag (point_flag) that is the information indicating whetherthe leaf includes a three-dimensional point (S1650).

Note that in the present embodiment, an example has been shown in whichthe encoding type is switched per node, but the present embodiment isnot necessarily limited thereto. The encoding type may be fixed pervolume, space, or world unit. In this case, the three-dimensional dataencoding device may append encoding type information to headerinformation of the volume, space, or world.

As stated above, the three-dimensional data encoding device according tothe present embodiment: generates first information in which an N-ary (Nis an integer of 2 or higher) tree structure of a plurality ofthree-dimensional points included in three-dimensional data is expressedusing a first formula (location encoding); and generates a bitstreamincluding the first information. The first information includes piecesof three-dimensional point information (location code) each associatedwith a corresponding one of the plurality of three-dimensional points.The pieces of three-dimensional point information each include indexes(idx) each associated with a corresponding one of a plurality of levelsin the N-ary tree structure. The indexes each indicate a subblock, amongN subblocks belonging to a corresponding one of the plurality of levels,to which a corresponding one of the plurality of three-dimensionalpoints belongs.

In other words, the pieces of three-dimensional point information eachindicate a path until the corresponding one of the plurality ofthree-dimensional points in the N-ary tree structure. The indexes eachindicate a child node, among N child nodes belonging to a correspondinglayer (node), included on the path.

This enables the three-dimensional data encoding method to generate abitstream from which the three-dimensional points can be selectivelydecoded.

For example, the pieces of three-dimensional point information (locationcode) each include information (num_idx) indicating a total number ofthe indexes included in the piece of three-dimensional pointinformation. In other words, the information indicates a depth (layercount) until a corresponding three-dimensional point in the N-ary treestructure.

For example, the first information includes information (numPoint)indicating a total number of the pieces of three-dimensional pointinformation included in the first information. In other words, theinformation indicates a total number of three-dimensional pointsincluded in the N-ary tree structure.

For example, N is 8, and the indexes are each a 3-bit value.

For example, in the three-dimensional data encoding device, a firstencoding mode is used for generating the first information, and a secondencoding mode is used for (i) generating second information (occupancycode) in which the N-ary tree structure is expressed using a secondformula (occupancy encoding) and (ii) generating a bitstream includingthe second information. The second information includes pieces of 1-bitinformation each of which (i) is associated with a corresponding one ofa plurality of subblocks belonging to the plurality of levels in theN-ary tree structure and (ii) indicates whether a three-dimensionalpoint is present in the corresponding one of the plurality of subblocks.

For example, the three-dimensional data encoding device uses the firstencoding mode when a total number of the plurality of three-dimensionalpoints is lower than or equal to a predetermined threshold value, andthe second encoding mode may be used when the total number of theplurality of three-dimensional points is higher than the predeterminedthreshold value. This enables the three-dimensional data encoding methodto reduce a code amount of the bitstream.

For example, the first information and the second information eachinclude information (encoding mode information) indicating whether theN-ary tree structure is expressed using the first formula or the secondformula.

For example, as illustrated in FIG. 75 and the like, thethree-dimensional data encoding device uses the first encoding mode forone portion of the N-ary tree structure and the second encoding mode foranother portion of the N-ary tree structure.

For example, the three-dimensional data encoding device includes aprocessor and memory, the processor using the memory to perform theabove processes.

The three-dimensional data decoding device according to the presentembodiment obtains, from a bitstream, first information (location code)in which an N-ary (N is an integer of 2 or higher) tree structure of aplurality of three-dimensional points included in three-dimensional datais expressed using a first formula (location encoding). The firstinformation includes pieces of three-dimensional point information(location code) each associated with a corresponding one of theplurality of three-dimensional points. The pieces of three-dimensionalpoint information each include indexes (idx) each associated with acorresponding one of a plurality of levels in the N-ary tree structure.The indexes each indicate a subblock, among N subblocks belonging to acorresponding one of the plurality of levels, to which a correspondingone of the plurality of three-dimensional points belongs.

In other words, the pieces of three-dimensional point information eachindicate a path until the corresponding one of the plurality ofthree-dimensional points in the N-ary tree structure. The indexes eachindicate a child node, among N child nodes belonging to a correspondinglayer (node), included on the path.

The three-dimensional data decoding method further restores, using acorresponding one of the pieces of three-dimensional point information,a three-dimensional point associated with the corresponding one of thepieces of three-dimensional point information.

This enables the three-dimensional data decoding device to selectivelygenerate the three-dimensional points from the bitstream.

For example, the pieces of three-dimensional point information (locationcode) each include information (num_idx) indicating a total number ofthe indexes included in the piece of three-dimensional pointinformation. In other words, the information indicates a depth (layercount) until a corresponding three-dimensional point in the N-ary treestructure.

For example, the first information includes information (numPoint)indicating a total number of the pieces of three-dimensional pointinformation included in the first information. In other words, theinformation indicates a total number of three-dimensional pointsincluded in the N-ary tree structure.

For example, N is 8, and the indexes are each a 3-bit value.

For example, the three-dimensional data decoding device further obtains,from a bitstream, second information (occupancy code) in which an N-arytree structure is expressed using a second formula (occupancy encoding).The three-dimensional data decoding device restores the plurality ofthree-dimensional points using the second information. The secondinformation includes pieces of 1-bit information each of which (i) isassociated with a corresponding one of a plurality of subblocksbelonging to the plurality of levels in the N-ary tree structure and(ii) indicates whether a three-dimensional point is present in thecorresponding one of the plurality of subblocks.

For example, the first information and the second information eachinclude information (encoding mode information) indicating whether theN-ary tree structure is expressed using the first formula or the secondformula.

For example, as illustrated in FIG. 75 and the like, one portion of theN-ary tree structure is expressed using the first formula and anotherportion of the N-ary tree structure is expressed using the secondformula.

For example, the three-dimensional data decoding device includes aprocessor and memory, the processor using the memory to perform theabove processes.

Embodiment 10

In the present embodiment, another example of the method of encoding atree structure such as an octree structure will be described. FIG. 88 isa diagram illustrating an example of a tree structure according to thepresent embodiment. Specifically, FIG. 88 shows an example of a quadtreestructure.

A leaf including a three-dimensional point is referred to as a validleaf, and a leaf including no three-dimensional point is referred to asan invalid leaf. A branch having the number of valid leaves greater thanor equal to a threshold value is referred to as a dense branch. A branchhaving the number of valid leaves less than the threshold value isreferred to as a sparse branch.

A three-dimensional data encoding device calculates the number ofthree-dimensional points (i.e., the number of valid leaves) included ineach branch in a layer of a tree structure. FIG. 88 shows an example inwhich a threshold value is 5. In this example, two branches are presentin layer 1. Since the left branch includes seven three-dimensionalpoints, the left branch is determined as a dense branch. Since the rightbranch includes two three-dimensional points, the right branch isdetermined as a sparse branch;

FIG. 89 is a graph showing an example of the number of valid leaves (3Dpoints) of each branch in layer 5. The horizontal axis of FIG. 89indicates an index that is an identification number of the branch inlayer 5. As clearly shown in FIG. 89, specific branches include manythree-dimensional points, compared to other branches. Occupancy encodingis more effective for such dense branches than for sparse branches.

The following describes how occupancy encoding and location encoding areapplied. FIG. 90 is a diagram illustrating a relationship betweenencoding schemes to be applied and the number of three-dimensionalpoints (the number of valid leaves) included in each branch in layer 5.As illustrated in FIG. 90, the three-dimensional data encoding deviceapplies the occupancy encoding to dense branches, and applies thelocation encoding to sparse branches. As a result, it is possible toimprove the coding efficiency;

FIG. 91 is a diagram illustrating an example of a dense branch area inLiDAR data. As illustrated in FIG. 91, a three-dimensional point densitycalculated from the number of three-dimensional points included in eachbranch varies from area to area.

Separating dense three-dimensional points (branch) and sparsethree-dimensional points (branch) brings the following advantage. Athree-dimensional point density is higher with a decreasing distance toa LiDAR sensor. Consequently, separating branches in accordance withsparseness and denseness enables division in a distance direction. Suchdivision is effective for specific applications. Using a method otherthan the occupancy encoding is effective for sparse branches.

In the present embodiment, the three-dimensional data encoding deviceseparates an inputted three-dimensional point cloud into two or morethree-dimensional point sub-clouds, and applies a different encodingmethod to each of the two or more three-dimensional point sub-clouds.

For example, the three-dimensional data encoding device separates aninputted three-dimensional point cloud into three-dimensional pointsub-cloud A (dense three-dimensional point cloud: dense cloud) includinga dense branch, and three-dimensional point sub-cloud B (sparsethree-dimensional point cloud: sparse cloud). FIG. 92 is a diagramillustrating an example of three-dimensional point sub-cloud A (densethree-dimensional point cloud) including a dense branch which isseparated from the tree structure illustrated in FIG. 88. FIG. 93 is adiagram illustrating an example of three-dimensional point sub-cloud B(sparse three-dimensional point cloud) including a sparse branch whichis separated from the tree structure illustrated in FIG. 88.

Next, the three-dimensional data encoding device encodesthree-dimensional point sub-cloud A using the occupancy encoding, andencodes three-dimensional point sub-cloud B using the location encoding.

It should be noted that although the example has been described above inwhich different encoding schemes (the occupancy encoding and thelocation encoding) are applied as different encoding methods, forexample, the three-dimensional data encoding device may apply the sameencoding scheme to three-dimensional point sub-cloud A andthree-dimensional point sub-cloud B, and may use different parameters inencoding three-dimensional point sub-cloud A and three-dimensional pointsub-cloud B.

The following describes a procedure for a three-dimensional dataencoding process performed by the three-dimensional data encodingdevice. FIG. 94 is a flowchart of a three-dimensional data encodingprocess performed by the three-dimensional data encoding deviceaccording to the present embodiment.

First, the three-dimensional data encoding device separates an inputtedthree-dimensional point cloud into three-dimensional point sub-clouds(S1701). The three-dimensional data encoding device may perform thisseparation automatically or based on information inputted by a user. Forexample, the user may specify a range of three-dimensional pointsub-clouds. As for an example of automatic separation, for example, wheninput data is LiDAR data, the three-dimensional data encoding deviceperforms the separation using distance information indicating a distanceto each point cloud. Specifically, the three-dimensional data encodingdevice separates point clouds within a certain range from a measurementpoint, and point clouds outside the certain range. In addition, thethree-dimensional data encoding device may perform the separation usinginformation indicating, for example, important areas and unimportantareas.

Next, the three-dimensional data encoding device generates encoded data(encoded bitstream) by encoding three-dimensional point sub-cloud Ausing method A (S1702). Besides, the three-dimensional data encodingdevice generates encoded data by encoding three-dimensional pointsub-cloud B using method B (S1703). It should be noted that thethree-dimensional data encoding device may encode three-dimensionalpoint sub-cloud B using method A. In this case, the three-dimensionaldata encoding device encodes three-dimensional point sub-cloud B using aparameter different from an encoding parameter used in encodingthree-dimensional point sub-cloud A. For example, this parameter may bea quantization parameter. For example, the three-dimensional dataencoding device encodes three-dimensional point sub-cloud B using aquantization parameter greater than a quantization parameter used inencoding three-dimensional point sub-cloud A. In this case, thethree-dimensional data encoding device may append information indicatinga quantization parameter used in encoding each of three-dimensionalpoint sub-clouds, to a header of encoded data of the three-dimensionalpoint sub-cloud.

Then, the three-dimensional data encoding device generates a bitstreamby combining the encoded data obtained in step S1702 and the encodeddata obtained in step S1703 (S1704).

Moreover, the three-dimensional data encoding device may encode, asheader information of the bitstream, information for decoding eachthree-dimensional point sub-cloud. For example, the three-dimensionaldata encoding device may encode information as described below.

The header information may include information indicating the number ofencoded three-dimensional sub-points. In this example, this informationindicates 2.

The header information may include information indicating the number ofthree-dimensional points included in each three-dimensional pointsub-cloud, and encoding methods. In this example, this informationindicates the number of three-dimensional points included inthree-dimensional point sub-cloud A, the encoding method (method A)applied to three-dimensional point sub-cloud A, the number ofthree-dimensional points included in three-dimensional point sub-cloudB, and the encoding method (method B) applied to three-dimensional pointsub-cloud B.

The header information may include information for identifying the startposition or end position of encoded data of each three-dimensional pointsub-cloud.

Moreover, the three-dimensional data encoding device may encodethree-dimensional point sub-cloud A and three-dimensional pointsub-cloud B in parallel. Alternatively, the three-dimensional dataencoding device may encode three-dimensional point sub-cloud A andthree-dimensional point sub-cloud B in sequence.

A method of separation into three-dimensional point sub-clouds is notlimited to the above method. For example, the three-dimensional dataencoding device changes a separation method, performs encoding usingeach of separation methods, and calculates the coding efficiency ofencoded data obtained using each separation method. Subsequently, thethree-dimensional data encoding device selects a separation methodhaving the highest coding efficiency from the separation methods. Forexample, the three-dimensional data encoding device may (i) separatethree-dimensional point clouds in each of layers, (ii) calculate codingefficiency in each of the cases, (iii) select a separation method (i.e.,a layer in which separation is performed) having the highest codingefficiency from separation methods, (iv) generate three-dimensionalpoint sub-clouds using the selected separation method, and (v) performencoding.

Moreover, when combining encoded data, the three-dimensional dataencoding device may place encoding information of a more importantthree-dimensional point sub-cloud in a position closer to the head of abitstream. Since this enables a three-dimensional data decoding deviceto obtain important information by only decoding the head of thebitstream, the three-dimensional data decoding device can obtain theimportant information quickly.

The following describes a procedure for a three-dimensional datadecoding process performed by the three-dimensional data decodingdevice. FIG. 95 is a flowchart of a three-dimensional data decodingprocess performed by the three-dimensional data decoding deviceaccording to the present embodiment.

First, for example, the three-dimensional data decoding device obtains abitstream generated by the above three-dimensional data encoding device.Next, the three-dimensional data decoding device separates, from theobtained bitstream, encoded data of three-dimensional point sub-cloud Aand encoded data of three-dimensional point sub-cloud B (S1711).Specifically, the three-dimensional data decoding device decodes, fromheader information of the bitstream, information for decoding eachthree-dimensional point sub-cloud, and separates encoded data of eachthree-dimensional point sub-cloud using the information.

Then, the three-dimensional data decoding device obtainsthree-dimensional point sub-cloud A by decoding the encoded data ofthree-dimensional point sub-cloud A using method A (S1712). In addition,the three-dimensional data decoding device obtains three-dimensionalpoint sub-cloud B by decoding the encoded data of three-dimensionalpoint sub-cloud B using method B (S1713). After that, thethree-dimensional data decoding device combines three-dimensional pointsub-cloud A and three-dimensional point sub-cloud B (S1714).

It should be noted that the three-dimensional data decoding device maydecode three-dimensional point sub-cloud A and three-dimensional pointsub-cloud B in parallel. Alternatively, the three-dimensional datadecoding device may decode three-dimensional point sub-cloud A andthree-dimensional point sub-cloud B in sequence.

Moreover, the three-dimensional data decoding device may decode anecessary three-dimensional point sub-cloud. For example, thethree-dimensional data decoding device may decode three-dimensionalpoint sub-cloud A and need not decode three-dimensional point sub-cloudB. For example, when three-dimensional point sub-cloud A is athree-dimensional point cloud included in an important area of LiDARdata, the three-dimensional data decoding device decodes thethree-dimensional point cloud included in the important area.Self-location estimation etc. in a vehicle or the like is performedusing the three-dimensional point cloud included in the important area.

The following describes a specific example of an encoding processaccording to the present embodiment. FIG. 96 is a flowchart of athree-dimensional data encoding process performed by thethree-dimensional data encoding device according to the presentembodiment.

First, the three-dimensional data encoding device separates inputtedthree-dimensional points into a sparse three-dimensional point cloud anda dense three-dimensional point cloud (S1721). Specifically, thethree-dimensional data encoding device counts the number of valid leavesof a branch in a layer of an octree structure. The three-dimensionaldata encoding device sets each branch as a dense branch or a sparsebranch in accordance with the number of valid leaves of the branch.Subsequently, the three-dimensional data encoding device generates athree-dimensional point sub-cloud (a dense three-dimensional pointcloud) obtained by gathering dense branches, and a three-dimensionalpoint sub-cloud (a sparse three-dimensional point cloud) obtained bygathering sparse branches.

Next, the three-dimensional data encoding device generates encoded databy encoding the sparse three-dimensional point cloud (S1722). Forexample, the three-dimensional data encoding device encodes a sparsethree-dimensional point cloud using the location encoding.

Furthermore, the three-dimensional data encoding device generatesencoded data by encoding the dense three-dimensional point cloud(S1723). For example, the three-dimensional data encoding device encodesa dense three-dimensional point cloud using the occupancy encoding.

Then, the three-dimensional data encoding device generates a bitstreamby combining the encoded data of the sparse three-dimensional pointcloud obtained in step S1722 and the encoded data of the densethree-dimensional point cloud obtained in step S1723 (S1724).

Moreover, the three-dimensional data encoding device may encode, asheader information of the bitstream, information for decoding the sparsethree-dimensional point cloud and the dense three-dimensional pointcloud. For example, the three-dimensional data encoding device mayencode information as described below.

The header information may include information indicating the number ofencoded three-dimensional point sub-clouds. In this example, thisinformation indicates 2.

The header information may include information indicating the number ofthree-dimensional points included in each three-dimensional pointsub-cloud, and encoding methods. In this example, this informationindicates the number of three-dimensional points included in the sparsethree-dimensional point cloud, the encoding method (location encoding)applied to the sparse three-dimensional point cloud, the number ofthree-dimensional points included in the dense three-dimensional pointcloud, and the encoding method (occupancy encoding) applied to the densethree-dimensional point cloud.

The header information may include information for identifying the startposition or end position of encoded data of each three-dimensional pointsub-cloud. In this example, this information indicates at least one ofthe start position and end position of the encoded data of the sparsethree-dimensional point cloud or the start position and end position ofthe encoded data of the dense three-dimensional point cloud.

Moreover, the three-dimensional data encoding device may encode thesparse three-dimensional point cloud and the dense three-dimensionalpoint cloud in parallel. Alternatively, the three-dimensional dataencoding device may encode the sparse three-dimensional point cloud andthe dense three-dimensional point cloud in sequence.

The following describes a specific example of a three-dimensional datadecoding process. FIG. 97 is a flowchart of a three-dimensional datadecoding process performed by the three-dimensional data decoding deviceaccording to the present embodiment.

First, for example, the three-dimensional data decoding device obtains abitstream generated by the above three-dimensional data encoding device.Next, the three-dimensional data decoding device separates, from theobtained bitstream, encoded data of a sparse three-dimensional pointcloud and encoded data of a dense three-dimensional point cloud (S1731).Specifically, the three-dimensional data decoding device decodes, fromheader information of the bitstream, information for decoding eachthree-dimensional point sub-cloud, and separates encoded data of eachthree-dimensional point sub-cloud using the information. In thisexample, the three-dimensional data decoding device separates, from thebitstream, the encoded data of the sparse three-dimensional point cloudand the encoded data of the dense three-dimensional point cloud usingthe header information.

Then, the three-dimensional data decoding device obtains the sparsethree-dimensional point cloud by decoding the encoded data of the sparsethree-dimensional point cloud (S1732). For example, thethree-dimensional data decoding device decodes the sparsethree-dimensional point cloud using location decoding for decodingencoded data obtained as a result of the location encoding.

In addition, the three-dimensional data decoding device obtains thedense three-dimensional point cloud by decoding the encoded data of thedense three-dimensional point cloud (S1733). For example, thethree-dimensional data decoding device decodes the densethree-dimensional point cloud using occupancy decoding for decodingencoded data obtained as a result of the occupancy encoding.

After that, the three-dimensional data decoding device combines thesparse three-dimensional point cloud obtained in step S1732 and thedense three-dimensional point cloud obtained in step S1733 (S1734).

It should be noted that the three-dimensional data decoding device maydecode the sparse three-dimensional point cloud and the densethree-dimensional point cloud in parallel. Alternatively, thethree-dimensional data decoding device may decode the sparsethree-dimensional point cloud and the dense three-dimensional pointcloud in sequence.

Moreover, the three-dimensional data decoding device may decode part ofnecessary three-dimensional point sub-clouds. For example, thethree-dimensional data decoding device may decode a densethree-dimensional point cloud and need not decode a sparsethree-dimensional point cloud. For example, when a densethree-dimensional point cloud is a three-dimensional point cloudincluded in an important area of LiDAR data, the three-dimensional datadecoding device decodes the three-dimensional point cloud included inthe important area. Self-location estimation etc. in a vehicle or thelike is performed using the three-dimensional point cloud included inthe important area;

FIG. 98 is a flowchart of an encoding process according to the presentembodiment. First, the three-dimensional data encoding separates aninputted three-dimensional point cloud into a sparse three-dimensionalpoint cloud and a dense three-dimensional point cloud (S1741).

Next, the three-dimensional data encoding device generates encoded databy encoding the dense three-dimensional point cloud (S1742). Then, thethree-dimensional data encoding device generates encoded data byencoding the sparse three-dimensional point cloud (S1743). Finally, thethree-dimensional data encoding device generates a bitstream bycombining the encoded data of the sparse three-dimensional point cloudobtained in step S1742 and the encoded data of the densethree-dimensional point cloud obtained in step S1743 (S1744);

FIG. 99 is a flowchart of a decoding process according to the presentembodiment. First, the three-dimensional data decoding device extracts,from a bitstream, encoded data of a sparse three-dimensional point cloudand encoded data of a dense three-dimensional (S1751). Next, thethree-dimensional data decoding device obtains decoded data of the densethree-dimensional point cloud by decoding the encoded data of the densethree-dimensional point cloud (S1752). Then, the three-dimensional datadecoding device obtains decoded data of the sparse three-dimensionalpoint cloud by decoding the encoded data of the sparse three-dimensionalpoint cloud (S1753). Finally, the three-dimensional data decoding devicegenerates a three-dimensional point cloud by combining the decoded dataof the dense three-dimensional point cloud obtained in step S1752 andthe decoded data of the sparse three-dimensional point cloud obtained instep S1753 (S1754).

It should be noted that the three-dimensional data encoding device andthe three-dimensional data decoding device may encode and decode any oneof a dense three-dimensional point cloud and a sparse three-dimensionalpoint cloud first. In addition, encoding processes or decoding processesmay be performed in parallel using processors etc.

Moreover, the three-dimensional data encoding device may encode one of adense three-dimensional point cloud and a sparse three-dimensional pointcloud. For example, when a dense three-dimensional point cloud includesimportant information, the three-dimensional data encoding deviceextracts the dense three-dimensional point cloud and a sparsethree-dimensional point cloud from an inputted three-dimensional pointcloud, and encode the dense three-dimensional point cloud but does notencode the sparse three-dimensional point cloud. This enables thethree-dimensional data encoding device to append the importantinformation to a stream while reducing an amount of bit. For example,when, between a server and a client, the client sends to the server atransmission request for three-dimensional point cloud information aboutthe surroundings of the client, the server encodes important informationabout the surroundings of the client as a dense three-dimensional pointcloud and transmits the encoded important information to the client.This enables the server to transmit the information requested by theclient while reducing a network bandwidth.

Moreover, the three-dimensional data decoding device may decode one of adense three-dimensional point cloud and a sparse three-dimensional pointcloud. For example, when a dense three-dimensional point cloud includesimportant information, the three-dimensional data decoding devicedecodes the dense three-dimensional point cloud but does not decode asparse three-dimensional point cloud. This enables the three-dimensionaldata decoding device to obtain necessary information while reducing aprocessing load of the decoding process;

FIG. 100 is a flowchart of the process of separating three-dimensionalpoints (S1741) illustrated in FIG. 98. First, the three-dimensional dataencoding device sets layer L and threshold value TH (S1761). It shouldbe noted that the three-dimensional data encoding device may appendinformation indicating set layer L and threshold value TH, to abitstream. In other words, the three-dimensional data encoding devicemay generate a bitstream including information indicating set layer Land threshold value TH.

Next, the three-dimensional data encoding device moves a target positionfrom a root of an octree to a lead branch in layer L. In other words,the three-dimensional data encoding device selects the lead branch inlayer L as a current branch (S1762).

Then, the three-dimensional data encoding device counts the number ofvalid leaves of the current branch inlayer L (S1763). When the number ofthe valid leaves of the current branch is greater than threshold valueTH (YES in S1764), the three-dimensional data encoding device registersthe current branch as a dense branch with a dense three-dimensionalpoint cloud (S1765). In contrast, when the number of the valid leaves ofthe current branch is less than threshold value TH (NO in S1764), thethree-dimensional data encoding device registers the current branch as asparse branch with a sparse three-dimensional point cloud (S1766).

When processing of all branches in layer L is not completed (NO inS1767), the three-dimensional data encoding device moves the targetposition to the next branch in layer L. In other words, thethree-dimensional data encoding device selects the next branch in layerL as a current branch (S1768). And then, the three-dimensional dataencoding device performs step S1763 and the subsequent steps on theselected next current branch.

The above-described process is repeated until the processing of all thebranches in layer L is completed (YES in S1767).

It should be noted that although layer L and threshold value TH arepreset in the above description, the present embodiment is notnecessarily limited to this. For example, the three-dimensional dataencoding device sets different combinations of layer L and thresholdvalue TH, generates a dense three-dimensional point cloud and a sparsethree-dimensional point cloud using each of the combinations, andencodes the dense three-dimensional point cloud and the sparsethree-dimensional point cloud. The three-dimensional data encodingdevice finally encodes the dense three-dimensional point cloud and thesparse three-dimensional point cloud using, among the combinations, acombination of layer L and threshold value TH having the highest codingefficiency for encoded data generated. This makes it possible to improvethe coding efficiency. Moreover, for example, the three-dimensional dataencoding device may calculate layer L and threshold value TH. Forexample, the three-dimensional data encoding device may set, to layer L,a value half as much as the maximum value of layers included in a treestructure. Furthermore, the three-dimensional data encoding device mayset, to threshold value TH, a value half as much as a total number ofthree-dimensional points included in the tree structure.

In the above description, the example has been shown in which theinputted three-dimensional point cloud is separated into two types ofthree-dimensional point cloud, that is, the dense three-dimensionalpoint cloud and the sparse three-dimensional point cloud. Thethree-dimensional data encoding device, however, may separate theinputted three-dimensional point cloud into at least three types ofthree-dimensional point cloud. For example, when the number of validleaves of a current branch is greater than or equal to first thresholdvalue TH1, the three-dimensional data encoding device classifies thecurrent branch into a first dense three-dimensional point cloud, andwhen the number of the valid leaves of the current branch is less thanfirst threshold value TH1 and greater than or equal to second thresholdvalue TH2, the three-dimensional data encoding device classifies thecurrent branch into a second dense three-dimensional point cloud. Whenthe number of the valid leaves of the current branch is less than secondthreshold value TH2 and greater than or equal to third threshold valueTH3, the three-dimensional data encoding device classifies the currentbranch into a first sparse three-dimensional point cloud, and when thenumber of the valid leaves of the current branch is less than thirdthreshold value TH3, the three-dimensional data encoding deviceclassifies the current branch into a second sparse three-dimensionalpoint cloud.

The following describes an example of a syntax of encoded data of athree-dimensional point cloud according to the present embodiment. FIG.101 is a diagram illustrating an example of this syntax. pc_header( )is, for example, header information of inputted three-dimensionalpoints.

num_sub_pc illustrated in FIG. 101 indicates the number ofthree-dimensional point sub-clouds. numPoint[i] indicates the number ofthree-dimensional points included in the i-th three-dimensional pointsub-cloud. coding_type[i] is coding type information indicating a codingtype (an encoding scheme) applied to the i-th three-dimensional pointsub-cloud. For example, coding_type=00 indicates that the locationencoding has been applied. coding_type=01 indicates that the occupancyencoding has been applied. coding_type=10 or 11 indicates that anotherencoding scheme has been applied.

data_sub_cloud( ) is encoded data of the i-th three-dimensional pointsub-cloud. coding_type_00_data is encoded data to which a coding type of00 indicated by coding_type has been applied, and is encoded data towhich the location encoding has been applied, for example.coding_type_01_data is encoded data to which a coding type of 01indicated by coding_type has been applied, and is encoded data to whichthe occupancy encoding has been applied, for example.

end_of_data is end information indicating the end of encoded data. Forexample, a constant bit sequence not used for encoded data is assignedto end_of_data. This enables the three-dimensional data decoding deviceto, for example, skip decoding of encoded data that need not be decoded,by searching a bitstream for a bit sequence of end_of_data.

It should be noted that the three-dimensional data encoding device mayentropy encode the encoded data generated by the above-described method.For example, the three-dimensional data encoding device binarizes eachvalue and performs arithmetic coding on the binarized value.

Although the example of the quadtree structure or the octree structurehas been shown in the present embodiment, the present embodiment is notnecessarily limited to this. The above-described method may be appliedto an N-ary (N is an integer greater than or equal to 2) tree, such as abinary tree and a hexadecatree, or another tree structure.

Variation

In the above example, as illustrated in FIG. 92 and FIG. 93, the treestructure is encoded that includes the dense branch and the upper layer(the tree structure from the root of the whole tree structure to theroot of the dense branch), and the tree structure is encoded thatincludes the sparse branch and the upper layer (the tree structure fromthe root of the whole tree structure to the root of the sparse branch).In the present variation, the three-dimensional data encoding deviceseparates a dense branch and a sparse branch, and encodes the densebranch and the sparse branch. In other words, a tree structure to beencoded does not include a tree structure of an upper layer. Forexample, the three-dimensional data encoding device applies theoccupancy encoding to a dense branch, and applies the location encodingto a sparse branch;

FIG. 102 is a diagram illustrating an example of a dense branchseparated from the tree structure illustrated in FIG. 88. FIG. 103 is adiagram illustrating an example of a sparse branch separated from thetree structure illustrated in FIG. 88. In the present variation, thetree structures illustrated in FIG. 102 and FIG. 103 are encoded.

The three-dimensional data encoding device encodes informationindicating a position of a branch instead of encoding a tree structureof an upper layer. For example, this information indicates a position ofa root of a branch.

For example, the three-dimensional data encoding device encodes, asencoded data of a dense branch, layer information indicating a layer inwhich the dense branch is generated, and branch information indicatingwhat number branch in the layer the dense branch is. This enables thethree-dimensional data decoding device to decode the layer informationand the branch information from a bitstream, and grasp whichthree-dimensional point cloud of what number branch in which layer thedecoded dense branch is. Likewise, the three-dimensional data encodingdevice encodes, as encoded data of a sparse branch, layer informationindicating a layer in which the sparse branch is generated, and branchinformation indicating what number branch in the layer the sparse branchis present, using these layer information and branch information.

This enables the three-dimensional data decoding device to decode thelayer information and the branch information from a bitstream, and graspwhich three-dimensional point cloud of what number branch in which layerthe decoded sparse branch is, using these layer information and branchinformation. Accordingly, since it is possible to reduce overheadresulting from encoding information of a layer higher than the densebranch or the sparse branch, it is possible to improve the codingefficiency.

It should be noted that branch information may indicate a value assignedto each branch in a layer indicated by layer information. Moreover,branch information may indicate a value assigned to each node from aroot of an octree as a starting point. In this case, layer informationneed not be encoded. Furthermore, the three-dimensional data encodingdevice may generate dense branches and sparse branches;

FIG. 104 is a flowchart of an encoding process according to the presentvariation. First, the three-dimensional data encoding device generatesone or more sparse branches and one or more dense branches from aninputted three-dimensional point cloud (S1771).

Next, the three-dimensional data encoding device generates encoded databy encoding each of the one or more dense branches (S1772). Then, thethree-dimensional data encoding device determines whether encoding ofall the dense branches generated in step S1771 is completed (S1774).

When the encoding of all the dense branches is not completed (NO inS1773), the three-dimensional data encoding device selects the nextdense branch (S1774) and generates encoded data by encoding the selecteddense branch (S1772).

On the other hand, when the encoding of all the dense branches iscompleted (YES in S1773), the three-dimensional data encoding devicegenerates encoded data by encoding each of the one or more sparsebranches (S1775). Next, the three-dimensional data encoding devicedetermines whether encoding of all the sparse branches generated in stepS1771 is completed (S1776).

When the encoding of all the sparse branches is not completed (NO inS1776), the three-dimensional data encoding device selects the nextsparse branch (S1777) and generates encoded data by encoding theselected sparse branch (S1775).

On the other hand, when the encoding of all the sparse branches iscompleted (YES in S1776), the three-dimensional data encoding devicecombines the encoded data generated in steps S1772 and S1775 to generatea bitstream (S1778);

FIG. 105 is a flowchart of a decoding process according to the presentvariation. First, the three-dimensional data decoding device extractsone or more encoded data items of respective dense branches, and one ormore encoded data items of respective sparse branches, from a bitstream(S1781). Next, the three-dimensional data decoding device obtainsdecoded data of each of the dense branches by decoding the encoded dataof the dense branch (S1782).

Then, the three-dimensional data decoding device determines whetherdecoding of the encoded data items of all the dense branches extractedin step S1781 is completed (S1783). When the decoding of the encodeddata items of all the dense branches is not completed (NO in S1783), thethree-dimensional data decoding device selects the encoded data of thenext dense branch (S1784) and obtains decoded data of the dense branchby decoding the selected encoded data of the dense branch (S1782).

On the other hand, when the decoding of the encoded data items of allthe dense branches is completed (YES in S1783), the three-dimensionaldata decoding device obtains decoded data of each of the sparse branchesby decoding the encoded data of the sparse branch (S1785).

After that, the three-dimensional data decoding device determineswhether decoding of the encoded data items of all the sparse branchesextracted in step S1781 is completed (S1786). When the decoding of theencoded data items of all the sparse branches is not completed (NO inS1786), the three-dimensional data decoding device selects the encodeddata of the next sparse branch (S1787) and obtains decoded data of thesparse branch by decoding the selected encoded data of the sparse branch(S1785).

On the other hand, when the decoding of the encoded data items of allthe sparse branches is completed (YES in S1786), the three-dimensionaldata decoding device combines the decoded data obtained in steps S1782and S1785 to generate a three-dimensional point cloud (S1788).

It should be noted that the three-dimensional data encoding device andthe three-dimensional data decoding device may encode and decode any oneof a dense branch and a sparse branch first. In addition, encodingprocesses or decoding processes may be performed in parallel usingprocessors etc.

Moreover, the three-dimensional data encoding device may encode one of adense branch and a sparse branch. In addition, the three-dimensionaldata encoding device may encode part of dense branches. For example,when a specific dense branch includes important information, thethree-dimensional data encoding device extracts dense branches andsparse branches from an inputted three-dimensional point cloud, andencodes the dense branch including the important information but doesnot encode the other dense branches and sparse branches. This enablesthe three-dimensional data encoding device to append the importantinformation to a stream while reducing an amount of bit. For example,when, between a server and a client, the client sends to the server atransmission request for three-dimensional point cloud information aboutthe surroundings of the client, the server encodes important informationabout the surroundings of the client as a dense branch and transmits theimportant information to the client. This enables the server to transmitthe information requested by the client while reducing a networkbandwidth.

Moreover, the three-dimensional data decoding device may decode one of adense branch and a sparse branch. In addition, the three-dimensionaldata decoding device may decode part of dense branches. For example,when a specific dense branch includes important information, thethree-dimensional data decoding device decodes the specific dense branchbut does not decode other dense branches and sparse branches. Thisenables the three-dimensional data decoding device to obtain necessaryinformation while reducing a processing load of the decoding process;

FIG. 106 is a flowchart of the process of separating three-dimensionalpoints (S1771) illustrated in FIG. 104. First, the three-dimensionaldata encoding device sets layer L and threshold value TH (S1761). Itshould be noted that the three-dimensional data encoding device mayappend information indicating set layer L and threshold value TH, to abitstream.

Next, the three-dimensional data encoding device selects a lead branchin layer L as a current branch (S1762). Then, the three-dimensional dataencoding device counts the number of valid leaves of the current branchin layer L (S1763). When the number of the valid leaves of the currentbranch is greater than threshold value TH (YES in S1764), thethree-dimensional data encoding device sets the current branch as adense branch, and appends layer information and branch information to abitstream (S1765A). On the other hand, when the number of the validleaves of the current branch is less than threshold value TH (NO inS1764), the three-dimensional data encoding device sets the currentbranch as a sparse branch, and appends layer information and branchinformation to a bitstream (S1766A).

When processing of all branches in layer L is not completed (NO inS1767), the three-dimensional data encoding device selects the nextbranch in layer L as a current branch (S1768). And then, thethree-dimensional data encoding device performs step S1763 and thesubsequent steps on the selected next current branch. Theabove-described process is repeated until the processing of all thebranches in layer L is completed (YES in S1767).

It should be noted that although layer L and threshold value TH arepreset in the above description, the present disclosure is notnecessarily limited to this. For example, the three-dimensional dataencoding device sets different combinations of layer L and thresholdvalue TH, generates a dense branch and a sparse branch using each of thecombinations, and encodes the dense branch and the sparse branch. Thethree-dimensional data encoding device finally encodes the dense branchand the sparse branch using, among the combinations, a combination oflayer L and threshold value TH having the highest coding efficiency forencoded data generated. This makes it possible to improve the codingefficiency. Moreover, for example, the three-dimensional data encodingdevice may calculate layer L and threshold value TH. For example, thethree-dimensional data encoding device may set, to layer L, a value halfas much as the maximum value of layers included in a tree structure.Furthermore, the three-dimensional data encoding device may set, tothreshold value TH, a value half as much as a total number ofthree-dimensional points included in the tree structure.

The following describes an example of a syntax of encoded data of athree-dimensional point cloud according to the present variation. FIG.107 is a diagram illustrating an example of this syntax. The example ofthe syntax illustrated in FIG. 107 is obtained by appending layer_id[i]that is layer information and branch_id[i] that is branch information,to the example of the syntax illustrated in FIG. 101.

layer_id[i] indicates a layer number of the i-th three-dimensional pointsub-cloud. branch_id[i] indicates a branch number in layer_id[i] of thei-th three-dimensional point sub-cloud.

layer_id[i] and branch_id[i] are layer information and branchinformation that indicate, for example, a position of a branch in anoctree. For example, layer_id[i]=2 and branch_id[i]=5 indicate that thei-th branch is the fifth branch in layer 2.

It should be noted that the three-dimensional data encoding device mayentropy encode the encoded data generated by the above-described method.For example, the three-dimensional data encoding device binarizes eachvalue and performs arithmetic coding on the binarized value.

Although the example of the quadtree structure or the octree structurehas been given in the present variation, the present disclosure is notnecessarily limited to this. The above-described method may be appliedto an N-ary (N is an integer greater than or equal to 2) tree, such as abinary tree and a hexadecatree, or another tree structure.

As stated above, the three-dimensional data encoding device according tothe present embodiment performs the process illustrated in FIG. 108.

First, the three-dimensional data encoding device generates an N-ary (Nis an integer greater than or equal to 2) tree structure ofthree-dimensional points included in three-dimensional data (S1801).

Next, the three-dimensional data encoding device generates first encodeddata by encoding, using a first encoding process, a first branch having,as a root, a first node included in a first layer that is one of layersincluded in the N-ary tree structure (S1802).

In addition, the three-dimensional data encoding device generates secondencoded data by encoding, using a second encoding process different fromthe first encoding process, a second branch having, as a root, a secondnode that is included in the first layer and different from the firstnode (S1803).

Then, the three-dimensional data encoding device generates a bitstreamincluding the first encoded data and the second encoded data (S1804).

Since this enables the three-dimensional data encoding device to applyan encoding process suitable for each branch included in the N-ary treestructure, it is possible to improve the coding efficiency.

For example, the number of three-dimensional points included in thefirst branch is less than a predetermined threshold value, and thenumber of three-dimensional points included in the second branch isgreater than the threshold value. In other words, when the number ofthree-dimensional points included in a current branch is less than athreshold value, the three-dimensional data encoding device sets thecurrent branch as the first branch, and when the number ofthree-dimensional points included in the current branch is greater thanthe threshold value, the three-dimensional data encoding device sets thecurrent branch as the second branch.

For example, the first encoded data includes first informationindicating that a first N-ary tree structure of first three-dimensionalpoints included in the first branch is expressed using a first formula.The second encoded data includes second information indicating that asecond N-ary tree structure of second three-dimensional points includedin the second branch is expressed using a second formula. In otherwords, the first encoding process and the second encoding process differin encoding scheme.

For example, the location encoding is used in the first encodingprocess, and the occupancy encoding is used in the second encodingprocess. In other words, the first information includes pieces ofthree-dimensional point information each of which is associated with acorresponding one of the first three-dimensional points. Each of thepieces of three-dimensional point information includes an indexassociated with each of layers in the first N-ary tree structure. Eachof the indexes indicates, among N sub-blocks belonging to acorresponding one of the layers, a sub-block to which a correspondingone of the first three-dimensional points belongs. The secondinformation includes pieces of 1-bit information each of which isassociated with a corresponding one of sub-blocks belonging to layers inthe second N-ary tree structure, and indicates whether athree-dimensional point is present in the corresponding sub-block.

For example, a quantization parameter used in the second encodingprocess is different from a quantization parameter used in the firstencoding process. In other words, the first encoding process and thesecond encoding process are identical in encoding scheme, but differ inparameter for use.

For example, as illustrated in FIG. 92 and FIG. 93, in the encoding ofthe first branch, the three-dimensional data encoding device encodes,using the first encoding process, the tree structure including the firstbranch and the tree structure from the root of the N-ary tree structureto the first node, and in the encoding of the second branch, thethree-dimensional data encoding device encodes, using the secondencoding process, the tree structure including the second branch and thetree structure from the root of the N-ary tree structure to the secondnode.

For example, the first encoded data includes encoded data of the firstbranch, and third information indicating a position of the first node inthe N-ary tree structure. The second encoded data includes encoded dataof the second branch, and fourth information indicating a position ofthe second node in the N-ary tree structure.

For example, the third information includes information (layerinformation) indicating the first layer, and information (branchinformation) indicating which one of nodes included in the first layerthe first node is. The fourth information includes the information(layer information) indicating the first layer, and information (branchinformation) indicating which one of nodes included in the first layerthe second node is.

For example, the first encoded data includes information (numPoint)indicating the number of three-dimensional points included in the firstbranch, and the second encoded data includes information (numPoint)indicating the number of three-dimensional points included in the secondbranch.

For example, the three-dimensional data encoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

The three-dimensional data decoding device according to the presentembodiment performs the process illustrated in FIG. 109.

First, the three-dimensional data decoding device obtains, from abitstream, first encoded data obtained by encoding a first branchhaving, as a root, a first node included in a first layer that is one oflayers included in an N-ary (N is an integer greater than or equal to 2)tree structure of three-dimensional points, and second encoded dataobtained by encoding a second branch having, as a root, a second nodethat is included in the first layer and different from the first node(S1811).

Next, the three-dimensional data decoding device generates first decodeddata of the first branch by decoding the first encoded data using afirst decoding process (S1812).

In addition, the three-dimensional data decoding device generates seconddecoded data of the second branch by decoding the second encoded datausing a second decoding process different from the first decodingprocess (S1813).

Then, the three-dimensional data decoding device restoresthree-dimensional points using the first decoded data and the seconddecoded data (S1814). For example, these three-dimensional pointsinclude three-dimensional points indicated by the first decoded data,and three-dimensional points indicated by the second decoded data.

This enables the three-dimensional data decoding device to decode thebitstream for which the coding efficiency is improved.

For example, the number of three-dimensional points included in thefirst branch is less than a predetermined threshold value, and thenumber of three-dimensional points included in the second branch isgreater than the threshold value.

For example, the first encoded data includes first informationindicating that a first N-ary tree structure of first three-dimensionalpoints included in the first branch is expressed using a first formula.The second encoded data includes second information indicating that asecond N-ary tree structure of second three-dimensional points includedin the second branch is expressed using a second formula. In otherwords, the first decoding process and the second decoding process differin encoding scheme (decoding scheme).

For example, the location encoding is used for the first encoded data,and the occupancy encoding is used for the second encoded data. In otherwords, the first information includes pieces of three-dimensional pointinformation each of which is associated with a corresponding one of thefirst three-dimensional points. Each of the pieces of three-dimensionalpoint information includes an index associated with each of layers inthe first N-ary tree structure. Each of the indexes indicates, among Nsub-blocks belonging to a corresponding one of the layers, a sub-blockto which a corresponding one of the first three-dimensional pointsbelongs. The second information includes pieces of 1-bit informationeach of which is associated with a corresponding one of sub-blocksbelonging to layers in the second N-ary tree structure, and indicateswhether a three-dimensional point is present in the correspondingsub-block.

For example, a quantization parameter used in the second decodingprocess is different from a quantization parameter used in the firstdecoding process. In other words, the first decoding process and thesecond decoding process are identical in encoding scheme (decodingscheme), but differ in parameter for use.

For example, as illustrated in FIG. 92 and FIG. 93, in the decoding ofthe first branch, the three-dimensional data decoding device decodes,using the first decoding process, the tree structure including the firstbranch and the tree structure from the root of the N-ary tree structureto the first node, and in the decoding of the second branch, thethree-dimensional data decoding device decodes, using the seconddecoding process, the tree structure including the second branch and thetree structure from the root of the N-ary tree structure to the secondnode.

For example, the first encoded data includes encoded data of the firstbranch, and third information indicating a position of the first node inthe N-ary tree structure. The second encoded data includes encoded dataof the second branch, and fourth information indicating a position ofthe second node in the N-ary tree structure.

For example, the third information includes information (layerinformation) indicating the first layer, and information (branchinformation) indicating which one of nodes included in the first layerthe first node is. The fourth information includes the information(layer information) indicating the first layer, and information (branchinformation) indicating which one of nodes included in the first layerthe second node is.

For example, the first encoded data includes information (numPoint)indicating the number of three-dimensional points included in the firstbranch, and the second encoded data includes information (numPoint)indicating the number of three-dimensional points included in the secondbranch.

For example, the three-dimensional data decoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

Embodiment 11

In the present embodiment, adaptive entropy encoding (arithmetic coding)performed on occupancy codes of an octree will be described;

FIG. 110 is a diagram illustrating an example of a quadtree structure.FIG. 111 is a diagram illustrating occupancy codes of the tree structureillustrated in FIG. 110. FIG. 112 is a diagram schematicallyillustrating an operation performed by a three-dimensional data encodingdevice according to the present embodiment.

The three-dimensional data encoding device according to the presentembodiment entropy encodes an 8-bit occupancy code in an octree. Thethree-dimensional data encoding device also updates a coding table in anentropy encoding process for occupancy code. Additionally, thethree-dimensional data encoding device does not use a single codingtable but uses an adaptive coding table in order to use similarityinformation of three-dimensional points. In other words, thethree-dimensional data encoding device uses coding tables.

Similarity information is, for example, geometry information of athree-dimensional point, structure information of an octree, orattribute information of a three-dimensional point.

It should be noted that although the quadtree is shown as the example inFIG. 110 to FIG. 112, the same method may be applied to an N-ary treesuch as a binary tree, an octree, and a hexadecatree. For example, thethree-dimensional data encoding device entropy encodes an 8-bitoccupancy code in the case of an octree, a 4-bit occupancy code in thecase of a quadtree, and a 16-bit occupancy code in the case of ahexadecatree, using an adaptive table (also referred to as a codingtable).

The following describes an adaptive entropy encoding process usinggeometry information of a three-dimensional point.

When local geometries of two nodes in a tree structure are similar toeach other, there is a chance that occupancy states (i.e., states eachindicating whether a three-dimensional point is included) of child nodesare similar to each other. As a result, the three-dimensional dataencoding device performs grouping using a local geometry of a parentnode. This enables the three-dimensional data encoding device to grouptogether the occupancy states of the child nodes, and use a differentcoding table for each group. Accordingly, it is possible to improve theentropy encoding efficiency;

FIG. 113 is a diagram illustrating an example of geometry information.Geometry information includes information indicating whether each ofneighboring nodes of a current node is occupied (i.e., includes athree-dimensional point). For example, the three-dimensional dataencoding device calculates a local geometry of the current node usinginformation indicating whether a neighboring node includes athree-dimensional point (is occupied or non-occupied). A neighboringnode is, for example, a node spatially located around a current node, ora node located in the same position in a different time as the currentnode or spatially located around the position.

In FIG. 113, a hatched cube indicates a current node. A white cube is aneighboring node, and indicates a node including a three-dimensionalpoint. In FIG. 113, the geometry pattern indicated in (2) is obtained byrotating the geometry pattern indicated in (1). Accordingly, thethree-dimensional data encoding device determines that these geometrypatterns have a high geometry similarity, and entropy encodes thegeometry patterns using the same coding table. In addition, thethree-dimensional data encoding device determines that the geometrypatterns indicated in (3) and (4) have a low geometry similarity, andentropy encodes the geometry patterns using other coding tables;

FIG. 114 is a diagram illustrating an example of occupancy codes ofcurrent nodes in the geometry patterns of (1) to (4) illustrated in FIG.113, and coding tables used for entropy encoding. As illustrated above,the three-dimensional data encoding device determines that the geometrypatterns of (1) and (2) are included in the same geometry group, anduses same coding table A for the geometry patterns of (1) and (2). Thethree-dimensional data encoding device uses coding table B and codingtable C for the geometry patterns of (3) and (4), respectively.

As illustrated in FIG. 114, there is a case in which the occupancy codesof the current nodes in the geometry patterns of (1) and (2) included inthe same geometry group are identical to each other.

Next, the following describes an adaptive entropy encoding process usingstructure information of a tree structure. For example, structureinformation includes information indicating a layer to which a currentnode belongs;

FIG. 115 is a diagram illustrating an example of a tree structure.Generally speaking, a local shape of an object depends on a searchcriterion. For example, a tree structure tends to be sparser in a lowerlayer than in an upper layer. Accordingly, the three-dimensional dataencoding device uses different coding tables for upper layers and lowerlayers as illustrated in FIG. 115, which makes it possible to improvethe entropy encoding efficiency.

In other words, when the three-dimensional data encoding device encodesan occupancy code of each layer, the three-dimensional data encodingdevice may use a different coding table for each layer. For example,when the three-dimensional data encoding device encodes an occupancycode of layer N (N=0 to 6), the three-dimensional data encoding devicemay perform entropy encoding on the tree structure illustrated in FIG.115 using a coding table for layer N. Since this enables thethree-dimensional data encoding device to select a coding table inaccordance with an appearance pattern of an occupancy code of eachlayer, the three-dimensional data encoding device can improve the codingefficiency.

Moreover, as illustrated in FIG. 115, the three-dimensional dataencoding device may use coding table A for the occupancy codes of layer0 to layer 2, and may use coding table B for the occupancy codes oflayer 3 to layer 6. Since this enables the three-dimensional dataencoding device to select a coding table in accordance with anappearance pattern of the occupancy code for each group of layers, thethree-dimensional data encoding device can improve the codingefficiency. The three-dimensional data encoding device may appendinformation of the coding table used for each layer, to a header of abitstream. Alternatively, the coding table used for each layer may bepredefined by standards etc.

Next, the following describes an adaptive entropy encoding process usingattribute information (property information) of a three-dimensionalpoint. For example, attribute information includes information about anobject including a current node, or information about a normal vector ofthe current node.

It is possible to group together three-dimensional points having asimilar geometry, using pieces of attribute information of thethree-dimensional points. For example, a normal vector indicating adirection of each of the three-dimensional points may be used as commonattribute information of the three-dimensional points. It is possible tofind a geometry relating to a similar occupancy code in a tree structureby using the normal vector.

Moreover, a color or a degree of reflection (reflectance) may be used asattribute information. For example, the three-dimensional data encodingdevice groups together three-dimensional points having a similargeometry, using the colors or reflectances of the three-dimensionalpoints, and performs a process such as switching between coding tablesfor each of the groups;

FIG. 116 is a diagram for describing switching between coding tablesbased on a normal vector. As illustrated in FIG. 116, when normal vectorgroups to which normal vectors of current nodes belong are different,different coding tables are used. For example, a normal vector includedin a predetermined range is categorized into one normal vector group.

When objects belong in different categories, there is a high possibilitythat occupancy codes are different. Accordingly, the three-dimensionaldata encoding device may select a coding table in accordance with acategory of an object to which a current node belongs. FIG. 117 is adiagram for describing switching between coding tables based on acategory of an object. As illustrated in FIG. 117, when objects belongin different categories, different coding tables are used.

The following describes an example of a structure of a bitstreamaccording to the present embodiment. FIG. 118 is a diagram illustratingan example of a structure of a bitstream generated by thethree-dimensional data encoding device according to the presentembodiment. As illustrated in FIG. 118, the bitstream includes a codingtable group, table indexes, and encoded occupancy codes. The codingtable group includes coding tables.

A table index indicates a coding table used for entropy encoding of asubsequent encoded occupancy code. An encoded occupancy code is anoccupancy code that has been entropy encoded. As illustrated in FIG.118, the bitstream also includes combinations of a table index and anencoded occupancy code.

For example, in the example illustrated in FIG. 118, encoded occupancycode 0 is data that has been entropy encoded using a context model (alsoreferred to as a context) indicated by table index 0. Encoded occupancycode 1 is data that has been entropy encoded using a context indicatedby table index 1. A context for encoding encoded occupancy code 0 may bepredefined by standards etc., and a three-dimensional data decodingdevice may use this context when decoding encoded occupancy code 0.Since this eliminates the need for appending the table index to thebitstream, it is possible to reduce overhead.

Moreover, the three-dimensional data encoding device may append, in theheader, information for resetting each context.

The three-dimensional data encoding device determines a coding tableusing geometry information, structure information, or attributeinformation of a current node, and encodes an occupancy code using thedetermined coding table. The three-dimensional data encoding deviceappends a result of the encoding and information (e.g., a table index)of the coding table used for the encoding to a bitstream, and transmitsthe bitstream to the three-dimensional data decoding device. Thisenables the three-dimensional data decoding device to decode theoccupancy code using the information of the coding table appended to theheader.

Moreover, the three-dimensional data encoding device need not appendinformation of a coding table used for encoding to a bitstream, and thethree-dimensional data decoding device may determine a coding tableusing geometry information, structure information, or attributeinformation of a current node that has been decoded, using the samemethod as the three-dimensional data encoding device, and decode anoccupancy code using the determined coding table. Since this eliminatesthe need for appending the information of the coding table to thebitstream, it is possible to reduce overhead;

FIG. 119 and FIG. 120 each are a diagram illustrating an example of acoding table. As illustrated in FIG. 119 and FIG. 120, one coding tableshows, for each value of an 8-bit occupancy code, a context model and acontext model type associated with the value.

As with the coding table illustrated in FIG. 119, the same context model(context) may be applied to occupancy codes. In addition, a differentcontext model may be assigned to each occupancy code. Since this enablesassignment of a context model in accordance with a probability ofappearance of an occupancy code, it is possible to improve the codingefficiency.

A context model type indicates, for example, whether a context model isa context model that updates a probability table in accordance with anappearance frequency of an occupancy code, or is a context model havinga fixed probability table.

Next, the following gives another example of a bitstream and a codingtable. FIG. 121 is a diagram illustrating a variation of a structure ofa bitstream. As illustrated in FIG. 121, the bitstream includes a codingtable group and an encoded occupancy code. The coding table groupincludes coding tables;

FIG. 122 and FIG. 123 each are a diagram illustrating an example of acoding table. As illustrated in FIG. 122 and FIG. 123, one coding tableshows, for each 1 bit included in an occupancy code, a context model anda context model type associated with the 1 bit;

FIG. 124 is a diagram illustrating an example of a relationship betweenan occupancy code and bit numbers of the occupancy code.

As stated above, the three-dimensional data encoding device may handlean occupancy code as binary data, assign a different context model foreach bit, and entropy encode the occupancy code. Since this enablesassignment of a context model in accordance with a probability ofappearance of each bit of the occupancy code, it is possible to improvethe coding efficiency.

Specifically, each bit of the occupancy code corresponds to a sub-blockobtained by dividing a spatial block corresponding to a current node.Accordingly, when sub-blocks in the same spatial position in a blockhave the same tendency, it is possible to improve the coding efficiency.For example, when a ground surface or a road surface crosses through ablock, in an octree, four lower blocks include three-dimensional points,and four upper blocks include no three-dimensional point. Additionally,the same pattern appears in blocks horizontally arranged. Accordingly,it is possible to improve the coding efficiency by switching betweencontexts for each bit as described above.

A context model that updates a probability table in accordance with anappearance frequency of each bit of an occupancy code may also be used.In addition, a context model having a fixed probability table may beused.

Next, the following describes procedures for a three-dimensional dataencoding process and a three-dimensional data decoding process accordingto the present embodiment;

FIG. 125 is a flowchart of a three-dimensional data encoding processincluding an adaptive entropy encoding process using geometryinformation.

In a decomposition process, an octree is generated from an initialbounding box of three-dimensional points. A bounding box is divided inaccordance with the position of a three-dimensional point in thebounding box. Specifically, a non-empty sub-space is further divided.Next, information indicating whether a sub-space includes athree-dimensional point is encoded into an occupancy code. It should benoted that the same process is performed in the processes illustrated inFIG. 127 and FIG. 129.

First, the three-dimensional data encoding device obtains inputtedthree-dimensional points (S1901). Next, the three-dimensional dataencoding device determines whether a decomposition process per unitlength is completed (S1902).

When the decomposition process per unit length is not completed (NO inS1902), the three-dimensional data encoding device generates an octreeby performing the decomposition process on a current node (S1903).

Then, the three-dimensional data encoding device obtains geometryinformation (S1904), and selects a coding table based on the obtainedgeometry information (S1905). Here, as stated above, the geometryinformation is information indicating, for example, a geometry ofoccupancy states of neighboring blocks of a current node.

After that, the three-dimensional data encoding device entropy encodesan occupancy code of the current node using the selected coding table(S1906).

Steps S1903 to S1906 are repeated until the decomposition process perunit length is completed. When the decomposition process per unit lengthis completed (YES in S1902), the three-dimensional data encoding deviceoutputs a bitstream including generated information (S1907).

The three-dimensional data encoding device determines a coding tableusing geometry information, structure information, or attributeinformation of a current node, and encodes a bit sequence of anoccupancy code using the determined coding table. The three-dimensionaldata encoding device appends a result of the encoding and information(e.g., a table index) of the coding table used for the encoding to abitstream, and transmits the bitstream to the three-dimensional datadecoding device. This enables the three-dimensional data decoding deviceto decode the occupancy code using the information of the coding tableappended to the header.

Moreover, the three-dimensional data encoding device need not appendinformation of a coding table used for encoding to a bitstream, and thethree-dimensional data decoding device may determine a coding tableusing geometry information, structure information, or attributeinformation of a current node that has been decoded, using the samemethod as the three-dimensional data encoding device, and decode anoccupancy code using the determined coding table. Since this eliminatesthe need for appending the information of the coding table to thebitstream, it is possible to reduce overhead;

FIG. 126 is a flowchart of a three-dimensional data decoding processincluding an adaptive entropy decoding process using geometryinformation.

A decomposition process included in the decoding process is similar tothe decomposition process included in the above-described encodingprocess, they differ in the following point. The three-dimensional datadecoding device divides an initial bounding box using a decodedoccupancy code. When the three-dimensional data decoding devicecompletes a process per unit length, the three-dimensional data decodingdevice stores the position of a bounding box as the position of athree-dimensional point. It should be noted that the same process isperformed in the processes illustrated in FIG. 128 and FIG. 130.

First, the three-dimensional data decoding device obtains an inputtedbitstream (S1911). Next, the three-dimensional data decoding devicedetermines whether a decomposition process per unit length is completed(S1912).

When the decomposition process per unit length is not completed (NO inS1912), the three-dimensional data decoding device generates an octreeby performing the decomposition process on a current node (S1913).

Then, the three-dimensional data decoding device obtains geometryinformation (S1914), and selects a coding table based on the obtainedgeometry information (S1915). Here, as stated above, the geometryinformation is information indicating, for example, a geometry ofoccupancy states of neighboring blocks of a current node.

After that, the three-dimensional data decoding device entropy decodesan occupancy code of the current node using the selected coding table(S1916).

Steps S1913 to S1916 are repeated until the decomposition process perunit length is completed. When the decomposition process per unit lengthis completed (YES in S1912), the three-dimensional data decoding deviceoutputs three-dimensional points (S1917);

FIG. 127 is a flowchart of a three-dimensional data encoding processincluding an adaptive entropy encoding process using structureinformation.

First, the three-dimensional data encoding device obtains inputtedthree-dimensional points (S1921). Next, the three-dimensional dataencoding device determines whether a decomposition process per unitlength is completed (S1922).

When the decomposition process per unit length is not completed (NO inS1922), the three-dimensional data encoding device generates an octreeby performing the decomposition process on a current node (S1923).

Then, the three-dimensional data encoding device obtains structureinformation (S1924), and selects a coding table based on the obtainedstructure information (S1925). Here, as stated above, the structureinformation is information indicating, for example, a layer to which acurrent node belongs.

After that, the three-dimensional data encoding device entropy encodesan occupancy code of the current node using the selected coding table(S1926).

Steps S1923 to S1926 are repeated until the decomposition process perunit length is completed. When the decomposition process per unit lengthis completed (YES in S1922), the three-dimensional data encoding deviceoutputs a bitstream including generated information (S1927);

FIG. 128 is a flowchart of a three-dimensional data decoding processincluding an adaptive entropy decoding process using structureinformation.

First, the three-dimensional data decoding device obtains an inputtedbitstream (S1931). Next, the three-dimensional data decoding devicedetermines whether a decomposition process per unit length is completed(S1932).

When the decomposition process per unit length is not completed (NO inS1932), the three-dimensional data decoding device generates an octreeby performing the decomposition process on a current node (S1933).

Then, the three-dimensional data decoding device obtains structureinformation (S1934), and selects a coding table based on the obtainedstructure information (S1935). Here, as stated above, the structureinformation is information indicating, for example, a layer to which acurrent node belongs.

After that, the three-dimensional data decoding device entropy decodesan occupancy code of the current node using the selected coding table(S1936).

Steps S1933 to S1936 are repeated until the decomposition process perunit length is completed. When the decomposition process per unit lengthis completed (YES in S1932), the three-dimensional data decoding deviceoutputs three-dimensional points (S1937);

FIG. 129 is a flowchart of a three-dimensional data encoding processincluding an adaptive entropy encoding process using attributeinformation.

First, the three-dimensional data encoding device obtains inputtedthree-dimensional points (S1941). Next, the three-dimensional dataencoding device determines whether a decomposition process per unitlength is completed (S1942).

When the decomposition process per unit length is not completed (NO inS1942), the three-dimensional data encoding device generates an octreeby performing the decomposition process on a current node (S1943).

Then, the three-dimensional data encoding device obtains attributeinformation (S1944), and selects a coding table based on the obtainedattribute information (S1945). Here, as stated above, the attributeinformation is information indicating, for example, a normal vector of acurrent node.

After that, the three-dimensional data encoding device entropy encodesan occupancy code of the current node using the selected coding table(S1946).

Steps S1943 to S1946 are repeated until the decomposition process perunit length is completed. When the decomposition process per unit lengthis completed (YES in S1942), the three-dimensional data encoding deviceoutputs a bitstream including generated information (S1947);

FIG. 130 is a flowchart of a three-dimensional data decoding processincluding an adaptive entropy decoding process using attributeinformation.

First, the three-dimensional data decoding device obtains an inputtedbitstream (S1951). Next, the three-dimensional data decoding devicedetermines whether a decomposition process per unit length is completed(S1952).

When the decomposition process per unit length is not completed (NO inS1952), the three-dimensional data decoding device generates an octreeby performing the decomposition process on a current node (S1953).

Then, the three-dimensional data encoding device obtains attributeinformation (S1954), and selects a coding table based on the obtainedattribute information (S1955). Here, as stated above, the attributeinformation is information indicating, for example, a normal vector of acurrent node.

After that, the three-dimensional data decoding device entropy decodesan occupancy code of the current node using the selected coding table(S1956).

Steps S1953 to S1956 are repeated until the decomposition process perunit length is completed. When the decomposition process per unit lengthis completed (YES in S1952), the three-dimensional data decoding deviceoutputs three-dimensional points (S1957);

FIG. 131 is a flowchart of the process of selecting a coding table usinggeometry information (S1905).

The three-dimensional data encoding device may select a coding table tobe used for entropy encoding of an occupancy code, using, as geometryinformation, information of a geometry group of a tree structure, forexample. Here, information of a geometry group is information indicatinga geometry group including a geometry pattern of a current node.

As illustrated in FIG. 131, when a geometry group indicated by geometryinformation is geometry group 0 (YES in S1961), the three-dimensionaldata encoding device selects coding table 0 (S1962). When the geometrygroup indicated by the geometry information is geometry group 1 (YES inS1963), the three-dimensional data encoding device selects coding table1 (S1964). In any other case (NO in S1963), the three-dimensional dataencoding device selects coding table 2 (S1965).

It should be noted that a method of selecting a coding table is notlimited to the above. For example, when a geometry group indicated bygeometry information is geometry group 2, the three-dimensional dataencoding device may further select a coding table according to a valueof the geometry group, such as using coding table 2.

For example, a geometry group is determined using occupancy informationindicating whether a node neighboring a current node includes a pointcloud. Geometry patterns that become the same shape by transform such asrotation being applied to may be included in the same geometry group.The three-dimensional data encoding device may select a geometry groupusing occupancy information of a node that neighbors a current node oris located around the current node, and belongs to the same layer as thecurrent node. In addition, the three-dimensional data encoding devicemay select a geometry group using occupancy information of a node thatbelongs to a layer different from that of a current node. For example,the three-dimensional data encoding device may select a geometry groupusing occupancy information of a parent node, a node neighboring theparent node, or a node located around the parent node.

It should be noted that the same applies to the process of selecting acoding table using geometry information (S1915) in the three-dimensionaldata decoding device;

FIG. 132 is a flowchart of the process of selecting a coding table usingstructure information (S1925).

The three-dimensional data encoding device may select a coding table tobe used for entropy encoding of an occupancy code, using, as structureinformation, layer information of a tree structure, for example. Here,the layer information indicates, for example, a layer to which a currentnode belongs.

As illustrated in FIG. 132, when a current node belongs to layer 0 (YESin S1971), the three-dimensional data encoding device selects codingtable 0 (S1972). When the current node belongs to layer 1 (YES inS1973), the three-dimensional data encoding device selects coding table1 (S1974). In any other case (NO in S1973), the three-dimensional dataencoding device selects coding table 2 (S1975).

It should be noted that a method of selecting a coding table is notlimited to the above. For example, when a current node belongs to layer2, the three-dimensional data encoding device may further select acoding table in accordance with the layer to which the current nodebelongs, such as using coding table 2.

The same applies to the process of selecting a coding table usingstructure information (S1935) in the three-dimensional data decodingdevice;

FIG. 133 is a flowchart of the process of selecting a coding table usingattribute information (S1945).

The three-dimensional data encoding device may select a coding table tobe used for entropy encoding of an occupancy code, using, as attributeinformation, information about an object to which a current node belongsor information about a normal vector of the current node.

As illustrated in FIG. 133, when a normal vector of a current nodebelongs to normal vector group 0 (YES in S1981), the three-dimensionaldata encoding device selects coding table 0 (S1982). When the normalvector of the current node belongs to normal vector group 1 (YES inS1983), the three-dimensional data encoding device selects coding table1 (S1984). In any other case (NO in S1983), the three-dimensional dataencoding device selects coding table 2 (S1985).

It should be noted that a method of selecting a coding table is notlimited to the above. For example, when a normal vector of a currentnode belongs to normal vector group 2, the three-dimensional dataencoding device may further select a coding table in accordance with anormal vector group to which the normal vector of the current belongs,such as using coding table 2.

For example, the three-dimensional data encoding device selects a normalvector group using information about a normal vector of a current node.For example, the three-dimensional data encoding device determines, asthe same normal vector group, normal vectors having a distance betweennormal vectors that is less than or equal to a predetermined thresholdvalue.

The information about the object to which the current node belongs maybe information about, for example, a person, a vehicle, or a building.

The following describes configurations of three-dimensional dataencoding device 1900 and three-dimensional data decoding device 1910according to the present embodiment. FIG. 134 is a block diagram ofthree-dimensional data encoding device 1900 according to the presentembodiment. Three-dimensional data encoding device 1900 illustrated inFIG. 134 includes octree generator 1901, similarity informationcalculator 1902, coding table selector 1903, and entropy encoder 1904.

Octree generator 1901 generates, for example, an octree from inputtedthree-dimensional points, and generates an occupancy code for each nodeincluded in the octree. Similarity information calculator 1902 obtains,for example, similarity information that is geometry information,structure information, or attribute information of a current node.Coding table selector 1903 selects a context to be used for entropyencoding of an occupancy code, according to the similarity informationof the current node. Entropy encoder 1904 generates a bitstream byentropy encoding the occupancy code using the selected context. Itshould be noted that entropy encoder 1904 may append, to the bitstream,information indicating the selected context;

FIG. 135 is a block diagram of three-dimensional data decoding device1910 according to the present embodiment. Three-dimensional datadecoding device 1910 illustrated in FIG. 135 includes octree generator1911, similarity information calculator 1912, coding table selector1913, and entropy decoder 1914.

Octree generator 1911 generates an octree in order from, for example, alower layer to an upper layer using information obtained from entropydecoder 1914. Similarity information calculator 1912 obtains similarityinformation that is geometry information, structure information, orattribute information of a current node. Coding table selector 1913selects a context to be used for entropy encoding of an occupancy code,according to the similarity information of the current node. Entropydecoder 1914 generates three-dimensional points by entropy decoding theoccupancy code using the selected context. It should be noted thatentropy decoder 1914 may obtain, by performing decoding, information ofthe selected context appended to a bitstream, and use the contextindicated by the information.

As illustrated in FIG. 122 to FIG. 124 above, the contexts are providedto the respective bits of the occupancy code. In other words, thethree-dimensional data encoding device entropy encodes a bit sequencerepresenting an N-ary (N is an integer greater than or equal to 2) treestructure of three-dimensional points included in three-dimensionaldata, using a coding table selected from coding tables. The bit sequenceincludes N-bit information for each node in the N-ary tree structure.The N-bit information includes N pieces of 1-bit information eachindicating whether a three-dimensional point is present in acorresponding one of N child nodes of a corresponding node. In each ofthe coding tables, a context is provided to each bit of the N-bitinformation. The three-dimensional data encoding device entropy encodeseach bit of the N-bit information using the context provided to the bitin the selected coding table.

This enables the three-dimensional data encoding device to improve thecoding efficiency by selecting a context for each bit.

For example, in the entropy encoding, the three-dimensional dataencoding device selects a coding table to be used from coding tables,based on whether a three-dimensional point is present in each ofneighboring nodes of a current node. This enables the three-dimensionaldata encoding device to improve the coding efficiency by selecting acoding table based on whether the three-dimensional point is present inthe neighboring node.

For example, in the entropy encoding, the three-dimensional dataencoding device (i) selects a coding table based on an arrangementpattern indicating an arranged position of a neighboring node in which athree-dimensional point is present, among neighboring nodes, and (ii)selects the same coding table for arrangement patterns that becomeidentical by rotation, among arrangement patterns. This enables thethree-dimensional data encoding device to reduce an increase in thenumber of coding tables.

For example, in the entropy encoding, the three-dimensional dataencoding device selects a coding table to be used from coding tables,based on a layer to which a current node belongs. This enables thethree-dimensional data encoding device to improve the coding efficiencyby selecting a coding table based on the layer to which the current nodebelongs.

For example, in the entropy encoding, the three-dimensional dataencoding device selects a coding table to be used from coding tables,based on a normal vector of a current node. This enables thethree-dimensional data encoding device to improve the coding efficiencyby selecting a coding table based on the normal vector.

For example, the three-dimensional data encoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

The three-dimensional data decoding device entropy decodes a bitsequence representing an N-ary (N is an integer greater than or equal to2) tree structure of three-dimensional points included inthree-dimensional data, using a coding table selected from codingtables. The bit sequence includes N-bit information for each node in theN-ary tree structure. The N-bit information includes N pieces of 1-bitinformation each indicating whether a three-dimensional point is presentin a corresponding one of N child nodes of a corresponding node. In eachof the coding tables, a context is provided to each bit of the N-bitinformation. The three-dimensional data decoding device entropy decodeseach bit of the N-bit information using the context provided to the bitin the selected coding table.

This enables the three-dimensional data decoding device to improve thecoding efficiency by selecting a context for each bit.

For example, in the entropy decoding, the three-dimensional datadecoding device selects a coding table to be used from coding tables,based on whether a three-dimensional point is present in each ofneighboring nodes of a current node. This enables the three-dimensionaldata decoding device to improve the coding efficiency by selecting acoding table based on whether the three-dimensional point is present inthe neighboring node.

For example, in the entropy decoding, the three-dimensional datadecoding device (i) selects a coding table based on an arrangementpattern indicating an arranged position of a neighboring node in which athree-dimensional point is present, among neighboring nodes, and (ii)selects the same coding table for arrangement patterns that becomeidentical by rotation, among arrangement patterns. This enables thethree-dimensional data decoding device to reduce an increase in thenumber of coding tables.

For example, in the entropy decoding, the three-dimensional datadecoding device selects a coding table to be used from coding tables,based on a layer to which a current node belongs. This enables thethree-dimensional data decoding device to improve the coding efficiencyby selecting a coding table based on the layer to which the current nodebelongs.

For example, in the entropy decoding, the three-dimensional datadecoding device selects a coding table to be used from coding tables,based on a normal vector of a current node. This enables thethree-dimensional data decoding device to improve the coding efficiencyby selecting a coding table based on the normal vector.

For example, the three-dimensional data decoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

Embodiment 12

In the present embodiment, a method of controlling reference when anoccupancy code is encoded will be described. It should be noted thatalthough the following mainly describes an operation of athree-dimensional data encoding device, a three-dimensional datadecoding device may perform the same process;

FIG. 136 and FIG. 137 each are a diagram illustrating a referencerelationship according to the present embodiment. Specifically, FIG. 136is a diagram illustrating a reference relationship in an octreestructure, and FIG. 137 is a diagram illustrating a referencerelationship in a spatial region.

In the present embodiment, when the three-dimensional data encodingdevice encodes encoding information of a current node to be encoded(hereinafter referred to as a current node), the three-dimensional dataencoding device refers to encoding information of each node in a parentnode to which the current node belongs. In this regard, however, thethree-dimensional data encoding device does not refer to encodinginformation of each node in another node (hereinafter referred to as aparent neighbor node) that is in the same layer as the parent node. Inother words, the three-dimensional data encoding device disables orprohibits reference to a parent neighbor node.

It should be noted that the three-dimensional data encoding device maypermit reference to encoding information of a parent node (hereinafteralso referred to as a grandparent node) of the parent node. In otherwords, the three-dimensional data encoding device may encode theencoding information of the current node by reference to the encodinginformation of each of the grandparent node and the parent node to whichthe current node belongs.

Here, encoding information is, for example, an occupancy code. When thethree-dimensional data encoding device encodes the occupancy code of thecurrent node, the three-dimensional data encoding device refers toinformation (hereinafter referred to as occupancy information)indicating whether a point cloud is included in each node in the parentnode to which the current node belongs. To put it in another way, whenthe three-dimensional data encoding device encodes the occupancy code ofthe current node, the three-dimensional data encoding device refers toan occupancy code of the parent node. On the other hand, thethree-dimensional data encoding device does not refer to occupancyinformation of each node in a parent neighbor node. In other words, thethree-dimensional data encoding device does not refer to an occupancycode of the parent neighbor node. Moreover, the three-dimensional dataencoding device may refer to occupancy information of each node in thegrandparent node. In other words, the three-dimensional data encodingdevice may refer to the occupancy information of each of the parent nodeand the parent neighbor node.

For example, when the three-dimensional data encoding device encodes theoccupancy code of the current node, the three-dimensional data encodingdevice selects a coding table to be used for entropy encoding of theoccupancy code of the current node, using the occupancy code of thegrandparent node or the parent node to which the current node belongs.It should be noted that the details will be described later. At thistime, the three-dimensional data encoding device need not refer to theoccupancy code of the parent neighbor node. Since this enables thethree-dimensional data encoding device to, when encoding the occupancycode of the current node, appropriately select a coding table accordingto information of the occupancy code of the parent node or thegrandparent node, the three-dimensional data encoding device can improvethe coding efficiency. Moreover, by not referring to the parent neighbornode, the three-dimensional data encoding device can suppress a processof checking the information of the parent neighbor node and reduce amemory capacity for storing the information. Furthermore, scanning theoccupancy code of each node of the octree in a depth-first order makesencoding easy.

The following describes an example of selecting a coding table using anoccupancy code of a parent node. FIG. 138 is a diagram illustrating anexample of a current node and neighboring reference nodes. FIG. 139 is adiagram illustrating a relationship between a parent node and nodes.FIG. 140 is a diagram illustrating an example of an occupancy code ofthe parent node. Here, a neighboring reference node is a node referredto when a current node is encoded, among nodes spatially neighboring thecurrent node. In the example shown in FIG. 138, the neighboring nodesbelong to the same layer as the current node. Moreover, node Xneighboring the current node in the x direction, node Y neighboring thecurrent block in the y direction, and node Z neighboring the currentblock in the z direction are used as the reference neighboring nodes. Inother words, one neighboring node is set as a reference neighboring nodein each of the x, y, and z directions.

It should be noted that the node numbers shown in FIG. 139 are oneexample, and a relationship between node numbers and node positions isnot limited to the relationship shown in FIG. 139. Although node 0 isassigned to the lowest-order bit and node 7 is assigned to thehighest-order bit in FIG. 140, assignments may be made in reverse order.In addition, each node may be assigned to any bit.

The three-dimensional data encoding device determines a coding table tobe used when the three-dimensional data encoding device entropy encodesan occupancy code of a current node, using the following equation, forexample.

CodingTable=(FlagX<<2)+(FlagY<<1)+(FlagZ)

Here, CodingTable indicates a coding table for an occupancy code of acurrent node, and indicates one of values ranging from 0 to 7. FlagX isoccupancy information of neighboring node X. FlagX indicates 1 whenneighboring node X includes a point cloud (is occupied), and indicates 0when it does not. FlagY is occupancy information of neighboring node Y.FlagY indicates 1 when neighboring node Y includes a point cloud (isoccupied), and indicates 0 when it does not. FlagZ is occupancyinformation of neighboring node Z. FlagZ indicates 1 when neighboringnode Z includes a point cloud (is occupied), and indicates 0 when itdoes not.

It should be noted that since information indicating whether aneighboring node is occupied is included in an occupancy code of aparent node, the three-dimensional data encoding device may select acoding table using a value indicated by the occupancy code of the parentnode.

From the foregoing, the three-dimensional data encoding device canimprove the coding efficiency by selecting a coding table using theinformation indicating whether the neighboring node of the current nodeincludes a point cloud.

Moreover, as illustrated in FIG. 138, the three-dimensional dataencoding device may select a neighboring reference node according to aspatial position of the current node in the parent node. In other words,the three-dimensional data encoding device may select a neighboring nodeto be referred to from the neighboring nodes, according to the spatialposition of the current node in the parent node.

Next, the following describes examples of configurations of thethree-dimensional data encoding device and the three-dimensional datadecoding device. FIG. 141 is a block diagram of three-dimensional dataencoding device 2100 according to the present embodiment.Three-dimensional data encoding device 2100 illustrated in FIG. 141includes octree generator 2101, geometry information calculator 2102,coding table selector 2103, and entropy encoder 2104.

Octree generator 2101 generates, for example, an octree from inputtedthree-dimensional points (a point cloud), and generates an occupancycode for each node included in the octree. Geometry informationcalculator 2102 obtains occupancy information indicating whether aneighboring reference node of a current node is occupied. For example,geometry information calculator 2102 obtains the occupancy informationof the neighboring reference node from an occupancy code of a parentnode to which the current node belongs. It should be noted that, asillustrated in FIG. 138, geometry information calculator 2102 may selecta neighboring reference node according to a position of the current nodein the parent node. In addition, geometry information calculator 2102does not refer to occupancy information of each node in a parentneighbor node.

Coding table selector 2103 selects a coding table to be used for entropyencoding of an occupancy code of the current node, using the occupancyinformation of the neighboring reference node calculated by geometryinformation calculator 2102. Entropy encoder 2104 generates a bitstreamby entropy encoding the occupancy code using the selected coding table.It should be noted that entropy encoder 2104 may append, to thebitstream, information indicating the selected coding table;

FIG. 142 is a block diagram of three-dimensional data decoding device2110 according to the present embodiment. Three-dimensional datadecoding device 2110 illustrated in FIG. 142 includes octree generator2111, geometry information calculator 2112, coding table selector 2113,and entropy decoder 2114.

Octree generator 2111 generates an octree of a space (nodes) usingheader information of a bitstream etc. Octree generator 2111 generatesan octree by, for example, generating a large space (a root node) usingthe size of a space along the x-axis, y-axis, and z-axis directionsappended to the header information, and generating eight small spaces A(nodes A0 to A7) by dividing the space into two along each of thex-axis, y-axis, and z-axis directions. Nodes A0 to A7 are set as acurrent node in sequence.

Geometry information calculator 2112 obtains occupancy informationindicating whether a neighboring reference node of a current node isoccupied. For example, geometry information calculator 2112 obtains theoccupancy information of the neighboring reference node from anoccupancy code of a parent node to which the current node belongs. Itshould be noted that, as illustrated in FIG. 138, geometry informationcalculator 2112 may select a neighboring reference node according to aposition of the current node in the parent node. In addition, geometryinformation calculator 2112 does not refer to occupancy information ofeach node in a parent neighboring node.

Coding table selector 2113 selects a coding table (a decoding table) tobe used for entropy decoding of the occupancy code of the current node,using the occupancy information of the neighboring reference nodecalculated by geometry information calculator 2112. Entropy decoder 2114generates three-dimensional points by entropy decoding the occupancycode using the selected coding table. It should be noted that codingtable selector 2113 may obtain, by performing decoding, information ofthe selected coding table appended to the bitstream, and entropy decoder2114 may use a coding table indicated by the obtained information.

Each bit of the occupancy code (8 bits) included in the bitstreamindicates whether a corresponding one of eight small spaces A (nodes A0to A7) includes a point cloud. Furthermore, the three-dimensional datadecoding device generates an octree by dividing small space node A0 intoeight small spaces B (nodes B0 to B7), and obtains informationindicating whether each node of small space B includes a point cloud, bydecoding the occupancy code. In this manner, the three-dimensional datadecoding device decodes the occupancy code of each node while generatingan octree by dividing a large space into small spaces.

The following describes procedures for processes performed by thethree-dimensional data encoding device and the three-dimensional datadecoding device. FIG. 143 is a flowchart of a three-dimensional dataencoding process in the three-dimensional data encoding device. First,the three-dimensional data encoding device determines (defines) a space(a current node) including part or whole of an inputtedthree-dimensional point cloud (S2101). Next, the three-dimensional dataencoding device generates eight small spaces (nodes) by dividing thecurrent node into eight (S2102). Then, the three-dimensional dataencoding device generates an occupancy code for the current nodeaccording to whether each node includes a point cloud (S2103).

After that, the three-dimensional data encoding device calculates(obtains) occupancy information of a neighboring reference node of thecurrent node from an occupancy code of a parent node of the current node(S2104). Next, the three-dimensional data encoding device selects acoding table to be used for entropy encoding, based on the calculatedoccupancy information of the neighboring reference node of the currentnode (S2105). Then, the three-dimensional data encoding device entropyencodes the occupancy code of the current node using the selected codingtable (S2106).

Finally, the three-dimensional data encoding device repeats a process ofdividing each node into eight and encoding an occupancy code of thenode, until the node cannot be divided (S2107). In other words, stepsS2102 to S2106 are recursively repeated;

FIG. 144 is a flowchart of a three-dimensional data decoding process inthe three-dimensional data decoding device. First, the three-dimensionaldata decoding device determines (defines) a space (a current node) to bedecoded, using header information of a bitstream (S2111). Next, thethree-dimensional data decoding device generates eight small spaces(nodes) by dividing the current node into eight (S2112). Then, thethree-dimensional data decoding device calculates (obtains) occupancyinformation of a neighboring reference node of the current node from anoccupancy code of a parent node of the current node (S2113).

After that, the three-dimensional data decoding device selects a codingtable to be used for entropy decoding, based on the occupancyinformation of the neighboring reference node (S2114). Next, thethree-dimensional data decoding device entropy decodes the occupancycode of the current node using the selected coding table (S2115).

Finally, the three-dimensional data decoding device repeats a process ofdividing each node into eight and decoding an occupancy code of thenode, until the node cannot be divided (S2116). In other words, stepsS2112 to S2115 are recursively repeated.

Next, the following describes an example of selecting a coding table.FIG. 145 is a diagram illustrating an example of selecting a codingtable. For example, as in coding table 0 shown in FIG. 145, the samecontext mode may be applied to occupancy codes. Moreover, a differentcontext model may be assigned to each occupancy code. Since this enablesassignment of a context model in accordance with a probability ofappearance of an occupancy code, it is possible to improve the codingefficiency. Furthermore, a context mode that updates a probability tablein accordance with an appearance frequency of an occupancy code may beused. Alternatively, a context model having a fixed probability tablemay be used.

It should be noted that although the coding tables illustrated in FIG.119 and FIG. 120 are used in the example shown in FIG. 145, the codingtables illustrated in FIG. 122 and FIG. 123 may be used instead.

Hereinafter, Variation 1 of the present embodiment will be described.FIG. 146 is a diagram illustrating a reference relationship in thepresent variation. Although the three-dimensional data encoding devicedoes not refer to the occupancy code of the parent neighbor node in theabove-described embodiment, the three-dimensional data encoding devicemay switch whether to refer to an occupancy code of a parent neighbornode, according to a specific condition.

For example, when the three-dimensional data encoding device encodes anoctree while scanning the octree breadth-first, the three-dimensionaldata encoding device encodes an occupancy code of a current node byreference to occupancy information of a node in a parent neighbor node.In contrast, when the three-dimensional data encoding device encodes theoctree while scanning the octree depth-first, the three-dimensional dataencoding device prohibits reference to the occupancy information of thenode in the parent neighbor node. By appropriately selecting a referablenode according to the scan order (encoding order) of nodes of the octreein the above manner, it is possible to improve the coding efficiency andreduce the processing load.

It should be noted that the three-dimensional data encoding device mayappend, to a header of a bitstream, information indicating, for example,whether an octree is encoded breadth-first or depth-first. FIG. 147 is adiagram illustrating an example of a syntax of the header information inthis case. octree_scan_order shown in FIG. 147 is encoding orderinformation (an encoding order flag) indicating an encoding order for anoctree. For example, when octree_scan_order is 0, breadth-first isindicated, and when octree_scan_order is 1, depth-first is indicated.Since this enables the three-dimensional data decoding device todetermine whether a bitstream has been encoded breadth-first ordepth-first by reference to octree_scan_order, the three-dimensionaldata decoding device can appropriately decode the bitstream

Moreover, the three-dimensional data encoding device may append, toheader information of a bitstream, information indicating whether toprohibit reference to a parent neighbor node. FIG. 148 is a diagramillustrating an example of a syntax of the header information in thiscase. limit_refer_flag is prohibition switch information (a prohibitionswitch flag) indicating whether to prohibit reference to a parentneighbor node. For example, when limit_refer_flag is 1, prohibition ofreference to the parent neighbor node is indicated, and whenlimit_refer_flag is 0, no reference limitation (permission of referenceto the parent neighbor node) is indicated.

In other words, the three-dimensional data encoding device determineswhether to prohibit the reference to the parent neighbor node, andselects whether to prohibit or permit the reference to the parentneighbor node, based on a result of the above determination. Inaddition, the three-dimensional data encoding device generates abitstream including prohibition switch information that indicates theresult of the determination and indicates whether to prohibit thereference to the parent neighbor node.

The three-dimensional data decoding device obtains, from a bitstream,prohibition switch information indicating whether to prohibit referenceto a parent neighbor node, and selects whether to prohibit or permit thereference to the parent neighbor node, based on the prohibition switchinformation.

This enables the three-dimensional data encoding device to control thereference to the parent neighbor node and generate the bitstream. Thatalso enables the three-dimensional data decoding device to obtain, fromthe header of the bitstream, the information indicating whether toprohibit the reference to the parent neighbor node.

Although the process of encoding an occupancy code has been described asan example of an encoding process in which reference to a parentneighbor node is prohibited in the present embodiment, the presentdisclosure is not necessarily limited to this. For example, the samemethod can be applied when other information of a node of an octree isencoded. For example, the method of the present embodiment may beapplied when other attribute information, such as a color, a normalvector, or a degree of reflection, added to a node is encoded.Additionally, the same method can be applied when a coding table or apredicted value is encoded.

Hereinafter, Variation 2 of the present embodiment will be described. Inthe above description, as illustrated in FIG. 138, the example in whichthe three reference neighboring nodes are used is given, but four ormore reference neighboring nodes may be used. FIG. 149 is a diagramillustrating an example of a current node and neighboring referencenodes.

For example, the three-dimensional data encoding device calculates acoding table to be used when the three-dimensional data encoding deviceentropy encodes an occupancy code of the current node shown in FIG. 149,using the following equation.

CodingTable=(FlagX0<<3)+(FlagX1<<2)+(FlagY<<1)+(FlagZ)

Here, CodingTable indicates a coding table for an occupancy code of acurrent node, and indicates one of values ranging from 0 to 15. FlagXNis occupancy information of neighboring node XN (N=0 . . . 1). FlaxXNindicates 1 when neighboring node XN includes a point cloud (isoccupied), and indicates 0 when it does not. FlagY is occupancyinformation of neighboring node Y. FlagY indicates 1 when neighboringnode Y includes a point cloud (is occupied), and indicates 0 when itdoes not. FlagZ is occupancy information of neighboring node Z. FlagZindicates 1 when neighboring node Z includes a point cloud (isoccupied), and indicates 0 when it does not.

At this time, when a neighboring node, for example, neighboring node X0in FIG. 149, is unreferable (prohibited from being referred to), thethree-dimensional data encoding device may use, as a substitute value, afixed value such as 1 (occupied) or 0 (unoccupied);

FIG. 150 is a diagram illustrating an example of a current node andneighboring reference nodes. As illustrated in FIG. 150, when aneighboring node is unreferable (prohibited from being referred to),occupancy information of the neighboring node may be calculated byreference to an occupancy code of a grandparent node of the currentnode. For example, the three-dimensional data encoding device maycalculate FlagX0 in the above equation using occupancy information ofneighboring node G0 instead of neighboring node X0 illustrated in FIG.150, and may determine a value of a coding table using calculatedFlagX0. It should be noted that neighboring node G0 illustrated in FIG.150 is a neighboring node occupancy or unoccupancy of which can bedetermined using the occupancy code of the grandparent node. Neighboringnode X1 is a neighboring node occupancy or unoccupancy of which can bedetermined using an occupancy code of a parent node.

Hereinafter, Variation 3 of the present embodiment will be described.FIG. 151 and FIG. 152 each are a diagram illustrating a referencerelationship according to the present variation. Specifically, FIG. 151is a diagram illustrating a reference relationship in an octreestructure, and FIG. 152 is a diagram illustrating a referencerelationship in a spatial region.

In the present variation, when the three-dimensional data encodingdevice encodes encoding information of a current node to be encoded(hereinafter referred to as current node 2), the three-dimensional dataencoding device refers to encoding information of each node in a parentnode to which current node 2 belongs. In other words, thethree-dimensional data encoding device permits reference to information(e.g., occupancy information) of a child node of a first node, amongneighboring nodes, that has the same parent node as a current node. Forexample, when the three-dimensional data encoding device encodes anoccupancy code of current node 2 illustrated in FIG. 151, thethree-dimensional data encoding device refers to an occupancy code of anode in the parent node to which current node 2 belongs, for example,the current node illustrated in FIG. 151. As illustrated in FIG. 152,the occupancy code of the current node illustrated in FIG. 151indicates, for example, whether each node in the current nodeneighboring current node 2 is occupied. Accordingly, since thethree-dimensional data encoding device can select a coding table for theoccupancy code of current node 2 in accordance with a more particularshape of the current node, the three-dimensional data encoding devicecan improve the coding efficiency.

The three-dimensional data encoding device may calculate a coding tableto be used when the three-dimensional data encoding device entropyencodes the occupancy code of current node 2, using the followingequation, for example.

CodingTable=(FlagX1<<5)+(FlagX2<<4)+(FlagX3<<3)+(FlagX4<<2)+(FlagY<<1)+(FlagZ)

Here, CodingTable indicates a coding table for an occupancy code ofcurrent node 2, and indicates one of values ranging from 0 to 63. FlagXNis occupancy information of neighboring node XN (N=1 . . . 4). FlagXNindicates 1 when neighboring node XN includes a point cloud (isoccupied), and indicates 0 when it does not. FlagY is occupancyinformation of neighboring node Y. FlagY indicates 1 when neighboringnode Y includes a point cloud (is occupied), and indicates 0 when itdoes not. FlagZ is occupancy information of neighboring node Z. FlagZindicates 1 when neighboring node Z includes a point cloud (isoccupied), and indicates 0 when it does not.

It should be noted that the three-dimensional data encoding device maychange a method of calculating a coding table, according to a nodeposition of current node 2 in the parent node.

When reference to a parent neighbor node is not prohibited, thethree-dimensional data encoding device may refer to encoding informationof each node in the parent neighbor node. For example, when thereference to the parent neighbor node is not prohibited, reference toinformation (e.g., occupancy information) of a child node of a thirdnode having a different parent node from that of a current node. In theexample illustrated in FIG. 150, for example, the three-dimensional dataencoding device obtains occupancy information of a child node ofneighboring node X0 by reference to an occupancy code of neighboringnode X0 having a different parent node from that of the current node.The three-dimensional data encoding device selects a coding table to beused for entropy encoding of an occupancy code of the current node,based on the obtained occupancy information of the child node ofneighboring node X0.

As stated above, the three-dimensional data encoding device according tothe present embodiment encodes information (e.g., an occupancy code) ofa current node included in an N-ary tree structure of three-dimensionalpoints included in three-dimensional data, where N is an integer greaterthan or equal to 2. As illustrated in FIG. 136 and FIG. 137, in theencoding, the three-dimensional data encoding device permits referenceto information (e.g., occupancy information) of a first node included inneighboring nodes spatially neighboring the current node, and prohibitsreference to information of a second node included in the neighboringnodes, the first node having a same parent node as the current node, thesecond node having a different parent node from the parent node of thecurrent node. To put it another way, in the encoding, thethree-dimensional data encoding device permits reference to information(e.g., an occupancy code) of the parent node, and prohibits reference toinformation (e.g., an occupancy code) of another node (a parent neighbornode) in the same layer as the parent node.

With this, the three-dimensional data encoding device can improve codingefficiency by reference to the information of the first node included inthe neighboring nodes spatially neighboring the current node, the firstnode having the same parent node as the current node. Besides, thethree-dimensional data encoding device can reduce a processing amount bynot reference to the information of the second node included in theneighboring nodes, the second node having a different parent node fromthe parent node of the current node. In this manner, thethree-dimensional data encoding device can not only improve the codingefficiency but also reduce the processing amount.

For example, the three-dimensional data encoding device furtherdetermines whether to prohibit the reference to the information of thesecond node. In the encoding, the three-dimensional data encoding deviceselects whether to prohibit or permit the reference to the informationof the second node, based on a result of the determining. Moreover, thethree-dimensional data encoding device generates a bit stream includingprohibition switch information (e.g., limit_refer_flag shown in FIG.148) that indicates the result of the determining and indicates whetherto prohibit the reference to the information of the second node.

With this, the three-dimensional data encoding device can select whetherto prohibit the reference to the information of the second node. Inaddition, a three-dimensional data decoding device can appropriatelyperform a decoding process using the prohibition switch information.

For example, the information of the current node is information (e.g.,an occupancy code) that indicates whether a three-dimensional point ispresent in each of child nodes belonging to the current node. Theinformation of the first node is information (the occupancy informationof the first node) that indicates whether a three-dimensional point ispresent in the first node. The information of the second node isinformation (the occupancy information of the second node) thatindicates whether a three-dimensional point is present in the secondnode.

For example, in the encoding, the three-dimensional data encoding deviceselects a coding table based on whether the three-dimensional point ispresent in the first node, and entropy encodes the information (e.g.,the occupancy code) of the current node using the coding table selected.

For example, as illustrated in FIG. 151 and FIG. 152, in the encoding,the three-dimensional data encoding device permits reference toinformation (e.g., occupancy information) of a child node of the firstnode, the child node being included in the neighboring nodes.

With this, since the three-dimensional data encoding device enablesreference to more detailed information of a neighboring node, thethree-dimensional data encoding device can improve the codingefficiency.

For example, as illustrated in FIG. 138, in the encoding, thethree-dimensional data encoding device selects a neighboring node to bereferred to from the neighboring nodes according to a spatial positionof the current node in the parent node.

With this, the three-dimensional data encoding device can refer to anappropriate neighboring node according to the spatial position of thecurrent node in the parent node.

For example, the three-dimensional data encoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

The three-dimensional data decoding device according to the presentembodiment decodes information (e.g., an occupancy code) of a currentnode included in an N-ary tree structure of three-dimensional pointsincluded in three-dimensional data, where N is an integer greater thanor equal to 2. As illustrated in FIG. 136 and FIG. 137, in the decoding,the three-dimensional data decoding device permits reference toinformation (e.g., occupancy information) of a first node included inneighboring nodes spatially neighboring the current node, and prohibitsreference to information of a second node included in the neighboringnodes, the first node having a same parent node as the current node, thesecond node having a different parent node from the parent node of thecurrent node. To put it another way, in the decoding, thethree-dimensional data decoding device permits reference to information(e.g., an occupancy code) of the parent node, and prohibits reference toinformation (e.g., an occupancy code) of another node (a parent neighbornode) in the same layer as the parent node.

With this, the three-dimensional data decoding device can improve codingefficiency by reference to the information of the first node included inthe neighboring nodes spatially neighboring the current node, the firstnode having the same parent node as the current node. Besides, thethree-dimensional data decoding device can reduce a processing amount bynot reference to the information of the second node included in theneighboring nodes, the second node having a different parent node fromthe parent node of the current node. In this manner, thethree-dimensional data decoding device can not only improve the codingefficiency but also reduce the processing amount.

For example, the three-dimensional data decoding device further obtains,from a bitstream, prohibition switch information (e.g., limit_refer_flagshown in FIG. 148) indicating whether to prohibit the reference to theinformation of the second node. In the decoding, the three-dimensionaldata decoding device selects whether to prohibit or permit the referenceto the information of the second node, based on the prohibition switchinformation.

With this, the three-dimensional data decoding device can appropriatelyperform a decoding process using the prohibition switch information.

For example, the information of the current node is information (e.g.,an occupancy code) that indicates whether a three-dimensional point ispresent in each of child nodes belonging to the current node. Theinformation of the first node is information (the occupancy informationof the first node) that indicates whether a three-dimensional point ispresent in the first node. The information of the second node isinformation (the occupancy information of the second node) thatindicates whether a three-dimensional point is present in the secondnode.

For example, in the decoding, the three-dimensional data encoding deviceselects a coding table based on whether the three-dimensional point ispresent in the first node, and entropy decodes the information (e.g.,the occupancy code) of the current node using the coding table selected.

For example, as illustrated in FIG. 151 and FIG. 152, in the decoding,the three-dimensional data decoding device permits reference toinformation (e.g., occupancy information) of a child node of the firstnode, the child node being included in the neighboring nodes.

With this, since the three-dimensional data decoding device enablesreference to more detailed information of a neighboring node, thethree-dimensional data decoding device can improve the codingefficiency.

For example, as illustrated in FIG. 138, in the decoding, thethree-dimensional data decoding device selects a neighboring node to bereferred to from the neighboring nodes according to a spatial positionof the current node in the parent node.

With this, the three-dimensional data decoding device can refer to anappropriate neighboring node according to the spatial position of thecurrent node in the parent node.

For example, the three-dimensional data decoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

Embodiment 13

Although the following mainly describes an operation of athree-dimensional data encoding device, a three-dimensional datadecoding device may perform the same process.

In the present embodiment, in the case where the three-dimensional dataencoding device encodes an inputted three-dimensional point cloud (apoint cloud) using an octree structure, when the three-dimensional dataencoding device repeats division until each leaf included in an octreehas a single three-dimensional point, and performs encoding, thethree-dimensional data encoding device appends, to a bitstream, modeinformation indicating whether each leaf of an octree includes a singlethree-dimensional point or one or more three-dimensional points. Inaddition, when the mode information is true (each leaf of the octreeincludes a single three-dimensional point), the three-dimensional dataencoding device does not encode leaf information about the leaf, andwhen the mode information is false (each leaf of the octree includes oneor more three-dimensional points), the three-dimensional data encodingdevice encodes the leaf information.

Here, the leaf information includes, for example, information indicatinghow many three-dimensional points a leaf includes, informationindicating relative coordinates etc. of a three-dimensional pointincluded in a leaf as illustrated in FIG. 61 to FIG. 67, or both.Accordingly, since it is unnecessary to encode the leaf information foreach leaf of the octree when the leaf includes a singlethree-dimensional point, it is possible to improve coding efficiency.When each leaf of the octree includes one or more three-dimensionalpoints, the three-dimensional data encoding device appropriately encodesand appends the leaf information to the bitstream. This enables thethree-dimensional data decoding device to correctly restore the one ormore three-dimensional points included in the leaf using the leafinformation;

FIG. 153 is a diagram illustrating an example of a syntax of headerinformation of a bitstream according to the present embodiment. Thisheader information is, for example, WLD, SPC, or VLM.single_point_per_leaf shown in FIG. 153 is information indicatingwhether each leaf of an octree includes a single three-dimensional pointor one or more three-dimensional points. Here, “each leaf of an octreeincludes a single three-dimensional point” means that all of the leavesincluded in the octree each include a single three-dimensional point(i.e., there is no leaf including two or more three-dimensional points).It should be noted that the octree here is, for example, a unit in whichmode information is appended, and corresponds to, for example, WLD, SPC,or VLM.

Furthermore, “each leaf of an octree includes one or morethree-dimensional points” means that at least one of the leaves includedin the octree includes two or more three-dimensional points. In otherwords, some of the leaves may include two or more three-dimensionalpoints, and the remaining leaves may each include a singlethree-dimensional point.

For example, that a value of mode information is 1 indicates each leafincluding a single three-dimensional point, and that a value of modeinformation is 0 indicates each leaf including one or morethree-dimensional points. It should be noted that even when all of theleaves included in the octree each include a single three-dimensionalpoint, the three-dimensional data encoding device may set modeinformation (single_point_per_leaf) to 0;

FIG. 154 is a diagram illustrating a configuration example of an octreewhen mode information indicates 1. As illustrated in FIG. 154, when themode information indicates 1, each leaf includes a singlethree-dimensional point. FIG. 155 is a diagram illustrating aconfiguration example of an octree when mode information indicates 0. Asillustrated in FIG. 155, when the mode information indicates 0, eachleaf includes a single three-dimensional point or two or morethree-dimensional points.

It should be noted that when a leaf includes two or morethree-dimensional points, for example, coordinates of the at two or morethree-dimensional points included in the leaf are different from eachother. Alternatively, the coordinates of the at two or morethree-dimensional points included in the leaf are identical, and piecesof attribute information, such as a color or a degree of reflection,(i.e., types of information) are mutually different. Alternatively, boththe coordinates of the two or more three-dimensional points included inthe leaf and the pieces of attribute information may be mutuallydifferent.

Next, an example of a syntax of leaf information will be described. Itshould be noted that although the example in which the mode informationis appended to the header of the bitstream has been given above, themode information need not be appended to the header, and standards or aprofile or level etc. of standards may specify whether each leaf of theoctree includes a single three-dimensional point or one or morethree-dimensional points. In this case, the three-dimensional datadecoding device can correctly restore the bitstream by, for example,determining whether each leaf of the octree includes a singlethree-dimensional point or one or more three-dimensional points, byreference to standards information included in the bitstream;

FIG. 156 is a diagram illustrating an example of a syntax of informationof each node included in an octree. isleaf shown in FIG. 156 is a flagindicating whether a node is a leaf. That isleaf is 1 indicates that anode is a leaf. That isleaf is 0 indicates that a node is not a leaf.

It should be noted that information indicating whether a node is a leafneed not be appended to a header. In this case, the three-dimensionaldata decoding device determines whether a node is a leaf using anothermethod. For example, the three-dimensional data decoding device maydetermine whether each node of the octree is divided into the smallestpossible size, and may determine that a node is a leaf when determiningthat each node is divided into the smallest possible size. Thiseliminates the need for encoding the flag indicating whether the node isthe leaf, which makes it possible to reduce the code amount of theheader.

num_point_per_leaf shown in FIG. 156 is leaf information and indicatesthe number of three-dimensional points included in a leaf.num_point_per_leaf is encoded when single_point_per_leaf==0, and is notencoded when single_point_per_leaf=1.

It should be noted that the three-dimensional data encoding device mayentropy encode num_point_per_leaf. At this time, the three-dimensionaldata encoding device may also perform encoding while switching codingtables. For example, the three-dimensional data encoding device mayperform arithmetic coding on the first bit of num_point_per_leaf usingcoding table A, and may perform arithmetic coding on the remaining bitsusing coding table B.

As stated above, the three-dimensional data encoding device may append,to the header of the bitstream, the mode information indicating whethereach leaf of the octree includes a single three-dimensional point or oneor more three-dimensional points, and may select whether to encode theleaf information (the information indicating the number ofthree-dimensional points included in the leaf) according to the value ofthe mode information. Besides, the three-dimensional data encodingdevice may encode, as the leaf information, positional information ofthe single or one or more three-dimensional points included in the leaf.

It should be noted that the three-dimensional data encoding device mayentropy encode single_point_per_leaf, isleaf, and num_point_per_leafgenerated by the above method. For example, the three-dimensional dataencoding device binarizes each value and performs arithmetic coding onthe binarized value.

Although the octree structure has been given as an example in thepresent embodiment, the present disclosure is not necessarily limited tothis. The aforementioned procedure may be applied to an N-ary treestructure such as a quadtree and a hexadecatree.

Moreover, when the three-dimensional data encoding device encodes, asthe leaf information, pieces of positional information of two or morethree-dimensional points in the same leaf, the three-dimensional dataencoding device may also encode pieces of attribute information (color,degree of reflectance, etc.) of the two or more three-dimensionalpoints. In this case, the pieces of positional information of the two ormore three-dimensional points and the pieces of attribute information ofthe same may be associated with each other. For example, when thethree-dimensional data encoding device encodes, as the leaf information,pieces of positional information of points A and B in the same leaf, thethree-dimensional data encoding device may encode pieces of attributeinformation of points A and B and append the pieces of attributeinformation to a bitstream. In other words, the leaf information mayinclude the positional information of point A, the attribute informationof point A, the positional information of point B, and the attributeinformation of point B. The pieces of positional information of points Aand B may be associated with the pieces of attribute information.

Moreover, the three-dimensional data encoding device may round off atleast M pieces of positional information of at least M three-dimensionalpoints in the same leaf, and may encode the at least M pieces ofpositional information as N pieces of positional information of Nthree-dimensional points, where N is less than M. In this case, thethree-dimensional data encoding device may round off at least M piecesof attribute information of the at least M three-dimensional points by,for example, averaging to generate N pieces of attribute information,and may encode the N pieces of attribute information generated. Forexample, the three-dimensional data encoding device may round off thepieces of positional information of points A and B in the same leaf to apiece of positional information of one point, and may encode the pieceof positional information. In this case, the three-dimensional dataencoding device may round off the pieces of attribute information ofpoints A and B by, for example, averaging to calculate a piece ofattribute information of one point, and may encode the piece ofattribute information calculated.

The following describes procedures performed by the three-dimensionaldata encoding device and three-dimensional data decoding deviceaccording to the present embodiment. FIG. 157 is a flowchart of athree-dimensional data encoding process performed by thethree-dimensional data encoding device according to the presentembodiment. First, the three-dimensional data encoding device determineswhether to perform encoding so that each leaf of an octree includes asingle three-dimensional point or to perform encoding so that each leafof the octree includes one or more three-dimensional points (S2201). Forexample, the three-dimensional data encoding device may determinewhether to perform encoding so that each leaf of the octree includes asingle three-dimensional point or to perform encoding so that each leafof the octree includes one or more three-dimensional points, accordingto whether to lossless encode an inputted three-dimensional point cloud.For example, when the three-dimensional data encoding device losslessencodes the inputted three-dimensional point cloud, thethree-dimensional data encoding device determines to perform encoding sothat each leaf of the octree includes a single three-dimensional point.Alternatively, the three-dimensional data encoding device may determinewhether to perform encoding so that each leaf of the octree includes asingle three-dimensional point or to perform encoding so that each leafof the octree includes one or more three-dimensional points, accordingto whether all the coordinates of the inputted three-dimensional pointsare mutually different and whether to perform encoding so that each ofthe three-dimensional points is included in a different leaf. Forexample, when the three-dimensional points include three-dimensionalpoints having the same coordinates, the three-dimensional data encodingdevice may determine to perform encoding so that each leaf of the octreeincludes one or more three-dimensional points.

When the three-dimensional data encoding device determines to performencoding so that each leaf of the octree includes a singlethree-dimensional point (YES in S2201), the three-dimensional dataencoding device sets mode information to a value indicating that eachleaf of the octree includes a single three-dimensional point(single_point_per_leaf=1), and appends the mode information to a header(S2202).

When the three-dimensional data encoding device determines to performencoding so that each leaf of the octree includes one or morethree-dimensional points (NO in S2201), the three-dimensional dataencoding device sets mode information to a value indicating that eachleaf of the octree includes one or more three-dimensional points(single_point_per_leaf=0), and appends the mode information to a header(S2203).

Next, the three-dimensional data encoding device generates an octreestructure by dividing a root node into an octree (S2204). At this time,when the mode information indicates that each leaf of the octree is toinclude a single three-dimensional point, the three-dimensional dataencoding device generates an octree in which each leaf of the octreeincludes a single three-dimensional point, and when the mode informationindicates that each leaf of the octree is to include one or morethree-dimensional points, the three-dimensional data encoding devicegenerates an octree in which each leaf of the octree includes one ormore three-dimensional points.

Then, the three-dimensional data encoding device selects a current nodeto be processed and determines whether the current node is a leaf(S2205). When the current node is the leaf (YES in S2205) and the modeinformation indicates that each leaf of the octree is to include one ormore three-dimensional points (single_point_per_leaf=0) (YES in S2206),the three-dimensional data encoding device encodes leaf informationindicating, for example, the number of three-dimensional points includedin the leaf (S2207).

In contrast, when the current node is the leaf (YES in S2205) and themode information indicates that each leaf of the octree is to include asingle three-dimensional point (single_point_per_leaf=1) (NO in S2206),the three-dimensional data encoding device does not encode leafinformation indicating, for example, the number of three-dimensionalpoints included in the leaf.

When the current node is the leaf (NO in S2205), the three-dimensionaldata encoding device encodes an occupancy code of the current node(S2208).

When processing of all nodes is not completed (NO in S2209), thethree-dimensional data encoding device selects the next current node andperforms step S2205 and the subsequent steps on the selected currentnode. When the processing of all the nodes is completed (YES in S2209),the three-dimensional data encoding device ends the process;

FIG. 158 is a flowchart of a three-dimensional data decoding processperformed by the three-dimensional data decoding device according to thepresent embodiment. First, the three-dimensional data decoding devicedecodes mode information (single_point_per_leaf) in the header of abitstream (S2211).

Next, the three-dimensional data decoding device generates an octree ofa space (nodes) using, for example, header information included in thebitstream (S2212). For example, the three-dimensional data decodingdevice generates a large space (a root node) using the size of a spacealong the x-axis, y-axis, and z-axis directions appended to the headerinformation. Subsequently, the three-dimensional data decoding devicegenerates an octree by generating eight small spaces (nodes A0 to A7) bydividing the space into two along each of the x-axis, y-axis, and z-axisdirections. In a similar way, the three-dimensional data decoding devicedivides each of nodes A0 to A7 into eight small spaces. Furthermore, thethree-dimensional data decoding device performs decoding of an occupancycode of each node and decoding of leaf information in sequence throughthe process illustrated in FIG. 158.

Specifically, the three-dimensional data decoding device selects acurrent node to be processed and determines whether the current node isa leaf (S2213). When the current node is the leaf (YES in S2213) and themode information indicates that each leaf of the octree is to includeone or more three-dimensional points (single_point_per_leaf=0) (YES inS2214), the three-dimensional data decoding device decodes leafinformation indicating, for example, the number of three-dimensionalpoints included in the leaf (S2215).

In contrast, when the current node is the leaf (YES in S2213) and themode information indicates that each leaf of the octree is to include asingle three-dimensional point (single_point_per_leaf=1) (NO in S2214),the three-dimensional data decoding device does not decode leafinformation indicating, for example, the number of three-dimensionalpoints included in the leaf.

When the current node is not the leaf (NO in S2213), thethree-dimensional data decoding device decodes an occupancy code of thecurrent node (S2216).

When processing of all nodes is not completed (NO in S2217), thethree-dimensional data decoding device selects the next current node andperforms step S2213 and the subsequent steps on the selected currentnode. When the processing of all the nodes is completed (YES in S2217),the three-dimensional data decoding device ends the process.

The following describes configurations of the three-dimensional dataencoding device and three-dimensional data decoding device according tothe present embodiment. FIG. 159 is a block diagram illustrating aconfiguration of three-dimensional data encoding device 2200 accordingto the present embodiment. Three-dimensional data encoding device 2200illustrated in FIG. 159 includes octree generator 2201, mode determiner2202, and entropy encoder 2203.

Octree generator 2201 generates, for example, an octree from inputtedthree-dimensional points (a point cloud), and generates a correspondingone of an occupancy code and leaf information for each node included inthe octree. Mode determiner 2202 determines whether to perform encodingso that each leaf of the octree includes a single three-dimensionalpoint or to perform encoding so that each leaf of the octree includesone or more three-dimensional points, and generates mode informationindicating a result of the determination. In other words, modedeterminer 2202 sets a value of single_point_per_leaf.

Entropy encoder 2203 encodes the leaf information according to the modeinformation to generate a bitstream. Additionally, entropy encoder 2203appends the leaf information (single_point_per_leaf) to the bitstream;

FIG. 160 is a block diagram illustrating a configuration ofthree-dimensional data decoding device 2210 according to the presentembodiment. Three-dimensional data decoding device 2210 illustrated inFIG. 160 includes octree generator 2211, mode information decoder 2212,and entropy decoder 2213.

Octree generator 2211 generates an octree of a space (nodes) using, forexample, header information of a bitstream. For example, octreegenerator 2211 generates a large space (a root node) using the size of aspace along the x-axis, y-axis, and z-axis directions appended to theheader information, and generates an octree by generating eight smallspaces (nodes A0 to A7) by dividing the space into two along each of thex-axis, y-axis, and z-axis directions. In a similar way, octreegenerator 2211 divides each of nodes A0 to A7 into eight small spaces.As stated above, octree generator 2211 repeats the generation of anoctree.

Mode information decoder 2212 decodes mode information(single_point_per_leaf) from the header information of the bitstream. Itshould be noted that mode information decoder 2212 may be included inentropy decoder 2213.

Entropy decoder 2213 decodes an occupancy code and leaf informationaccording to the mode information decoded, and generatesthree-dimensional points using the occupancy code and the leafinformation decoded.

As stated above, the three-dimensional data encoding device according tothe present embodiment performs the process illustrated in FIG. 161.First, the three-dimensional data encoding device appends, to abitstream, first information (mode information) indicating whether aleaf to be included in an N-ary tree structure of three-dimensionalpoints included in three-dimensional data is to include a singlethree-dimensional point or two or more three-dimensional points, where Nis an integer greater than or equal to 2 (S2221). In other words, thethree-dimensional data encoding device encodes the first information.

When the first information indicates that the leaf is to include asingle three-dimensional point (YES in S2222), the three-dimensionaldata encoding device generates an N-ary tree structure in which a leafincludes a single three-dimensional point (S2223), and encodes the N-arytree structure (S2224).

In contrast, when the first information indicates that the leaf is toinclude two or more three-dimensional points, the three-dimensional dataencoding device generates an N-ary tree structure in which a leafincludes two or more three-dimensional points (S2225), and encodes theN-ary tree structure (S2226).

With this, the three-dimensional data encoding device can selectivelyuse the tree structure in which the leaf includes a singlethree-dimensional point, and the tree structure in which the leafincludes two or more three-dimensional points. Accordingly, thethree-dimensional data encoding device can improve the codingefficiency.

For example, when the first information indicates that the leaf is toinclude two or more three-dimensional points, the three-dimensional dataencoding device appends second information about the leaf (leafinformation). When the first information indicates that the leaf is toinclude a single three-dimensional point, the three-dimensional dataencoding device appends no second information to the bitstream.

With this, the three-dimensional data encoding device can improve thecoding efficiency by appending no second information to the bitstreamwhen the leaf is to include a single three-dimensional point.

For example, the second information indicates a total number ofthree-dimensional points included in the leaf.

For example, the first information is commonly used by leaves. Forexample, the first information is commonly used by all or part of leavesto be included in an N-ary tree structure. In other words, the firstinformation indicates whether each of leaves to be included in the N-arytree structure is to include a single three-dimensional point or two ormore three-dimensional points. When the first information indicates thateach of the leaves is to include a single three-dimensional point, thethree-dimensional data encoding device generates an N-ary tree structurein which each of leaves includes a single three-dimensional point, andencodes the N-ary tree structure. When the first information indicatesthat each of the leaves is to include two or more three-dimensionalpoints, the three-dimensional data encoding device generates an N-arytree structure in which each of leaves includes two or morethree-dimensional points, and encodes the N-ary tree structure.

With this, since it is possible to control the formats of the leavesusing the single first information, the three-dimensional data encodingdevice can improve the coding efficiency.

For example, the two or more three-dimensional points included in theleaf have mutually different space coordinates. In other words, thesecond information may show the coordinates of each of the two or morethree-dimensional points included in the leaf.

For example, the two or more three-dimensional points included in theleaf have same space coordinates and mutually different attributeinformation. In other words, the second information may show theattribute information of each of the two or more three-dimensionalpoints included in the leaf.

For example, each of the two or more three-dimensional points includedin the leaf has coordinate information and attribute information. Inother words, the second information may show the coordinates and theattribute information of each of the two or more three-dimensionalpoints included in the leaf.

For example, the three-dimensional data encoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

The three-dimensional data decoding device according to the presentembodiment performs the process illustrated in FIG. 162. First, thethree-dimensional data decoding device decodes, from a bitstream, firstinformation (mode information) indicating whether a leaf to be includedin an N-ary tree structure of three-dimensional points included inthree-dimensional data is to include a single three-dimensional point ortwo or more three-dimensional points, where N is an integer greater thanor equal to 2 (S2231). In other words, the three-dimensional datadecoding device obtains the first information from the bitstream.

When the first information indicates that the leaf is to include asingle three-dimensional point (YES in S2232), the three-dimensionaldata decoding device decodes an N-ary tree structure in which a leafincludes a single three-dimensional point (S2233). In contrast, when thefirst information indicates that the leaf is to include two or morethree-dimensional points (NO in S2232), the three-dimensional datadecoding device decodes an N-ary tree structure in which a leaf includestwo or more three-dimensional points (S2234). Here, the phrase “todecode an N-ary tree structure in which a leaf includes a singlethree-dimensional point” means to parse information included in abitstream based on a rule created on, for example, a premise that a leafis to include only a single three-dimensional point. Likewise, thephrase “to decode an N-ary tree structure in which a leaf includes twoor more three-dimensional points” means to parse information included ina bitstream based on a rule created on, for example, a premise that aleaf is to include two or more three-dimensional points.

With this, the three-dimensional data decoding device can selectivelyuse the tree structure in which the leaf includes a singlethree-dimensional point, and the tree structure in which the leafincludes two or more three-dimensional points. Accordingly, thethree-dimensional data decoding device can improve the codingefficiency.

For example, when the first information indicates that the leaf is toinclude two or more three-dimensional points, the three-dimensional datadecoding device decodes (obtains), from the bitstream, secondinformation about the leaf (leaf information). When the firstinformation indicates that the leaf is to include a singlethree-dimensional point, the three-dimensional data decoding devicedecodes (obtains) no leaf information.

With this, since the second information need not be appended to thebitstream when the leaf is to include a single three-dimensional point,it is possible to improve the coding efficiency.

For example, the second information indicates a total number ofthree-dimensional points included in the leaf.

For example, the first information is commonly used by leaves. Forexample, the first information is commonly used by all or part of leavesto be included in an N-ary tree structure. In other words, the firstinformation indicates whether each of leaves to be included in the N-arytree structure is to include a single three-dimensional point or two ormore three-dimensional points. When the first information indicates thateach of the leaves is to include a single three-dimensional point, thethree-dimensional data decoding device generates an N-ary tree structurein which each of leaves includes a single three-dimensional point, anddecodes the N-ary tree structure. When the first information indicatesthat each of the leaves is to include two or more three-dimensionalpoints, the three-dimensional data decoding device generates an N-arytree structure in which each of leaves includes two or morethree-dimensional points, and decodes the N-ary tree structure.

With this, since it is possible to control the formats of the leavesusing the single first information, the three-dimensional data decodingdevice can improve the coding efficiency.

For example, the two or more three-dimensional points included in theleaf have mutually different space coordinates. In other words, thesecond information may show the coordinates of each of the two or morethree-dimensional points included in the leaf.

For example, the two or more three-dimensional points included in theleaf have same space coordinates and mutually different attributeinformation. In other words, the second information may show theattribute information of each of the two or more three-dimensionalpoints included in the leaf.

For example, each of the two or more three-dimensional points includedin the leaf has coordinate information and attribute information. Inother words, the second information may show the coordinates and theattribute information of each of the two or more three-dimensionalpoints included in the leaf.

For example, the three-dimensional data decoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

Embodiment 14

In the present embodiment, a three-dimensional data encoding deviceexpresses an occupancy code using a 1-bit occupied position and aremaining bit, and encodes each of the 1-bit occupied position and theremaining bit using a different method.

A 1-bit occupied position indicates a bit position at which 1 appearsfirst when each bit included in an occupancy code is scanned from theleft. For example, a 1-bit occupied position takes a value from 0 to 7for an octree, and takes a value from 0 to 15 for a hexadecatree.

A remaining bit indicates part of a bit sequence located on the rightside of a 1-bit occupied position of an occupancy code. The remainingbit has the number of bits ranging from 0 to 7 according to the 1-bitoccupied position;

FIG. 163 is a diagram illustrating examples of a 1-bit occupied positionand a remaining bit generated from an occupancy code. In the exampleshown by (a) in FIG. 163, the occupancy code is 01000010. Since 1appears first at the sixth bit when this occupancy code is scanned fromthe left, the 1-bit occupied position is 6 and the remaining bit is000010. In the example shown by (b) in FIG. 163, the occupancy code is00000010. Since 1 appears first at the first bit when this occupancycode is scanned from the left, the 1-bit occupied position is 1 and theremaining bit is 0. In the example shown by (c) in FIG. 163, theoccupancy code is 00000001. Since 1 appears first at the zeroth bit whenthis occupancy code is scanned from the left, the 1-bit occupiedposition is 0 and the remaining bit is absent.

Hereinafter, an example of a method of encoding a 1-bit occupiedposition will be described. In the event of an octree, thethree-dimensional data encoding device entropy encodes a 1-bit occupiedposition as a 3-bit value (0 to 7). The three-dimensional data encodingdevice performs, for example, arithmetic encoding on the 1-bit occupiedposition using one coding table. It should be noted that thethree-dimensional data encoding device may perform binary encoding(binary arithmetic encoding) one bit at a time on the 1-bit occupiedposition that is a 3-bit bit sequence. The three-dimensional dataencoding device may set a probability of occurrence of 0 and aprobability of occurrence of 1 to 50% in a coding table in this case.For example, the three-dimensional data encoding device may apply abypass mode in binary arithmetic encoding.

Next, an example of a method of encoding a remaining bit will bedescribed. For example, regarding a remaining bit as a binary bitsequence, the three-dimensional data encoding device performs binarycoding on bits in order from the left to the right. For example, when aremaining bit is 000010, the three-dimensional data encoding device mayperform arithmetic encoding on values of 0 and 1 in order of 0→0→0→1→0.

For example, in the example shown by (a) in FIG. 163, thethree-dimensional data encoding device performs arithmetic encoding on avalue of 6 at the 1-bit occupied position. For example, thethree-dimensional data encoding device may perform arithmetic encodingon a bit sequence of 110 indicating the value of 6, using the bypassmode. The three-dimensional data encoding device also performsarithmetic encoding on a bit sequence of 000010 of the remaining bit.

Moreover, in the example shown by (b) in FIG. 163, the three-dimensionaldata encoding device performs arithmetic encoding on a value of 1 at the1-bit occupied position. For example, the three-dimensional dataencoding device may perform arithmetic encoding on a bit sequence of 1indicating the value of 1, using the bypass mode. The three-dimensionaldata encoding device also performs arithmetic encoding on a bit sequenceof 0 of the remaining bit.

Furthermore, in the example shown by (c) in FIG. 163, thethree-dimensional data encoding device performs arithmetic encoding on avalue of 0 at the 1-bit occupied position. For example, thethree-dimensional data encoding device may perform arithmetic encodingon a bit sequence of 0 indicating the value of 0, using the bypass mode.Since the remaining bit is absent, the three-dimensional data encodingdevice encodes no remaining bit.

It should be noted that a 1-bit occupied position may be defined as abit position at which 1 appears first when each bit of an occupancy codeis scanned from the right. In this case, a remaining bit indicates partof a bit sequence located on the left side of the 1-bit occupiedposition of the occupancy code. Also, in this case, thethree-dimensional data encoding device may perform binary coding on theremaining bit in order from the right to the left. In addition, thethree-dimensional data encoding device may encode a switch flag forswitching between scanning each bit of the occupancy code from the rightand scanning each bit of the occupancy code from the left. Thethree-dimensional data encoding device may encode the switch flag foreach occupancy code. Accordingly, it is possible to change a scan orderfor each occupancy code. Additionally, the three-dimensional dataencoding device may add the switch flag to the header of a world, theheader of a space, or the header of a volume, etc. and change a scanorder on a world, space, or volume basis.

It should be noted that the scan order may be a predetermined order. Inaddition, a bit position at which 0 appears first may be used instead ofthe bit position at which 1 appears first in the scan order.

Moreover, an occupancy code in which only a 1 bit among bits included inthe occupancy code has a value of 1 is defined as a 1-bit occupied code.For example, in the event of the octree, the occupancy code “0010000” isa 1-bit occupied code, but the occupancy code “0010001” is not a 1-bitoccupied code.

The three-dimensional data encoding device may determine whether acurrent occupancy code to be encoded is likely to be a 1-bit occupiedcode. Then, the three-dimensional data encoding device may encode thecurrent occupancy code in a form of the 1-bit occupied position and aremaining bit (hereinafter referred to as occupied position encoding)when determining that the current occupancy code is likely to be the1-bit occupied code, and may encode a value of the current occupancycode (hereinafter referred to as direct encoding) directly whendetermining that the current occupancy code is not likely to be the1-bit occupied code.

For example, the three-dimensional data encoding device determineswhether a current occupancy code is likely to be a 1-bit occupied codeusing a value of an occupancy code of a parent node of a current node.For example, the three-dimensional data encoding device determineswhether the occupancy code of the parent node is a 1-bit occupied code;performs occupied position encoding on a occupancy code of a currentnode when determining that the occupancy code of the parent node is the1-bit occupied code; and performs direct encoding on the occupancy codeof the current node when determining that the occupancy code of theparent node is not the 1-bit occupied code.

Here, in the case where occupied position encoding is performed when thecurrent occupancy code of the current node is likely to be a 1-bitoccupied code, a value of each bit of the remaining bit tends to be 0.Accordingly, it is possible to improve the coding efficiency byperforming binary arithmetic encoding on the remaining bit. In addition,the three-dimensional data encoding device can efficiently determinewhether the current occupancy code is likely to be a 1-bit occupiedcode, based on whether the occupancy code of the parent node is a 1-bitoccupied code. Additionally, in the event of not a breadth-first codingorder but a depth-first coding order, it is possible to apply the samedetermination method by reference to the occupancy code of the parentnode;

FIG. 164 is a diagram schematically illustrating the above-mentionedprocess. As illustrated in FIG. 164, when the occupancy code of theparent node is a 1-bit occupied code, the three-dimensional dataencoding device performs occupied position encoding on the current node.Moreover, when the occupancy code of the parent node is a non-1-bitoccupied code (not a 1-bit occupied code), the three-dimensional dataencoding device performs direct encoding on the current node.

Next, an example of a syntax of information of a node will be described.FIG. 165 is a diagram illustrating an example of a syntax of informationof a node.

As illustrated in FIG. 165, the node information includes1bit_occupied_position and remaining_bit. 1bit_occupied_position is theabove-mentioned 1-bit occupied position and indicates a bit position atwhich 1 appears first when each bit of an occupancy code is scanned fromthe left. For example, the 1-bit occupied position takes a value from 0to 7 for the octree, and takes a value from 0 to 15 for thehexadecatree.

remaining_bit is the above-mentioned remaining bit and indicates part ofa bit sequence located on the right side of the 1-bit occupied positionof the occupancy code. Since a remaining bit is absent when a 1-bitoccupied position (1bit_occupied_position) is 0, remaining_bit need notbe encoded as illustrated in FIG. 165. Moreover, regarding remaining_bitas a binary bit sequence, the three-dimensional data encoding device mayperform binary coding on bits in order from the left to the right.Furthermore, the three-dimensional data encoding device may performarithmetic encoding on a decimal value calculated from the bit sequenceof remaining_bit, using a coding table. For example, when a bit sequenceof a remaining bit is 000010, the three-dimensional data encoding devicemay perform arithmetic encoding on a value of 2.

When an occupancy code (parent_occupancy_code) of a parent node is not a1-bit occupied code, the three-dimensional data encoding device mayperform direct encoding on the occupancy code. For example, thethree-dimensional data encoding device may perform arithmetic encodingon an occupancy code using one coding table.

It should be noted that although the octree structure has been describedas an example in the present embodiment, the present disclosure is notnecessarily limited to this. The aforementioned procedure may be appliedto an N-ary tree such as the quadtree and the hexadecatree, or othertree structures, where N is an integer greater than or equal to 2. Forexample, 1bit_occupied_position takes a value from 0 to 3 for thequadtree, and 1_bit_occupied_position takes a value from 0 to 15 for thehexadecatree. The three-dimensional data encoding device may encode, asa 2-bit occupied position (2bit_occupied_position), a position at which1 appears second when a bit sequence scanned, in addition to a 1-bitoccupied position; and may encode part of the bit sequence after the2-bit occupied position as a remaining bit. Additionally, thethree-dimensional data encoding device may encode, for example, as aN-bit occupied position (Nbit_occupied_position), a position at which 1appears for the nth time when a bit sequence is scanned; and may encodepart of the bit sequence after the N-bit occupied position as aremaining bit.

In the present embodiment, when an occupancy code of a current node islikely to be a 1-bit occupied code, the three-dimensional data encodingdevice performs occupied position encoding. In other words, thethree-dimensional data encoding device performs arithmetic encoding on,as a 1-bit occupied position, a bit position including values each ofwhich is 1 with a random probability, using, for example, coding tableA; and performs arithmetic encoding on, as a remaining bit, a remainingbit sequence including values each of which tends to be 0, using, forexample, coding table B. It is possible to improve the coding efficiencyby representing the occupancy code in different forms and usingdifferent coding tables for arithmetic encoding in such a manner. Forexample, the three-dimensional data encoding device can performarithmetic encoding on a bit sequence of a remaining bit while keeping aprobability of occurrence of values of 0 high, using coding table B.Even when an original bit sequence of the remaining bit has a greatlength, the three-dimensional data encoding device can reduce the numberof bits in encoded data as a result.

Each bit of a 1-bit occupied code tends to be a value of 1 with a randomprobability. As a result, the three-dimensional data encoding device mayperform arithmetic encoding on the 1-bit occupied code using a bypassmode that skips calculating an occurrence probability by setting aprobability of occurrence of 0 and a probability of occurrence of 1 to50%. Accordingly, it is possible to reduce the amount of processing.

It should be note that a three-dimensional data decoding device maydetermine whether occupied position encoding or direct encoding has beenperformed, through the same process as the three-dimensional dataencoding device. Alternatively, the three-dimensional data encodingdevice may generate a bitstream including information indicating whetheroccupied position encoding or direct encoding has been performed, andthe three-dimensional data decoding device may determine whetheroccupied position encoding or direct encoding has been performed, basedon the information included in the bitstream. In this case, thethree-dimensional data encoding device may also refer not to anoccupancy code of a parent node but to a current occupancy code, performoccupied position encoding when the current occupancy code is a 1-bitoccupied code, and perform direct encoding when the current occupancycode is not the 1-bit occupied code.

Also, although an example in which occupied position encoding and directencoding are switched on a node basis has been described in the presentembodiment, the present disclosure is not limited to this. For example,the three-dimensional data encoding device may add, to the header of aworld or the header of a space, etc., a flag indicating whether toperform occupied position encoding; and may select whether to performoccupied position encoding on a world or space etc. basis. For example,for a world or a space including many sparse three-dimensional pointclouds, the three-dimensional data encoding device may set the flag toON and perform occupied position encoding on all occupancy codes of thethree-dimensional point clouds in the world or the space. In addition,for a world or a space including many dense three-dimensional pointclouds, the three-dimensional data encoding device may set the flag toOFF and perform direct encoding on all occupancy codes of thethree-dimensional data point clouds in the world or the space. Thiseliminates the need for determining selection for each node, and it isthus possible to reduce the amount of processing.

Since the three-dimensional data decoding device can decode the flagincluded in the header such as the world or the space to determinewhether occupied position encoding or direct encoding has been performedon the occupancy code in the world or the space, the three-dimensionaldata decoding device can decode the occupancy code appropriately.

The three-dimensional data encoding device may perform occupied positionencoding when an occupancy code of a current node is likely to be aN-bit occupied code in which the number of bits having a value of 1included in the occupancy code is less than or equal to N (any integer),and may perform direct encoding when the occupancy code of the currentnode is not likely to be the N-bit occupied code. For example, thethree-dimensional data encoding device may perform occupied positionencoding when an occupancy code of a parent node is a N-bit occupiedcode, and may perform direct encoding when the occupancy code of theparent node is not the N-bit occupied code.

Hereinafter, a processing flow in the three-dimensional data encodingdevice will be described. FIG. 166 is a flowchart of a three-dimensionaldata encoding process performed by the three-dimensional data encodingdevice according to the present embodiment.

First, the three-dimensional data encoding device determines whether anoccupancy code of a parent node of a current node is a 1-bit occupiedcode (S2301). When the occupancy code of the parent node is the 1-bitoccupied code (YES in S2301), the three-dimensional data encoding deviceperforms occupied position encoding on a current occupancy code of thecurrent node (S2302).

Specifically, the three-dimensional data encoding device searches for a1-bit occupied position in the current occupancy code (S2304), andencodes the obtained 1-bit occupied position (S2305). Then, thethree-dimensional data encoding device calculates a remaining bit(S2306) and encodes the obtained remaining bit (S2307).

On the other hand, when the occupancy code of the parent node is not the1-bit occupied code (NO in S2301), the three-dimensional data encodingdevice performs direct encoding on the current occupancy code (S2303).

It should be noted that the order of the steps included in the occupiedposition encoding step (S2302) may be rearranged. For example, thethree-dimensional data encoding device may search for a 1-bit occupiedposition (S2304), calculate a remaining bit (S2306), and then encode the1-bit occupied position and the remaining bit (S2305, S2307);

FIG. 167 is a flowchart illustrating a specific example of the occupiedposition encoding step (S2302). First, the three-dimensional dataencoding device calculates a 1-bit occupied position (S2304).Specifically, the three-dimensional data encoding device sets variable ato 7 (S2311). Next, the three-dimensional data encoding device setsoccupancy code −2^(a) to variable Diff (S2312). Then, thethree-dimensional data encoding device determines whether Diff>−1 issatisfied (S2313).

When Diff>−1 is not satisfied (NO in S2313), the three-dimensional dataencoding device sets a−1 to variable a (S2314). When Diff>−1 issatisfied (YES in S2313), the three-dimensional data encoding devicesets a to a 1-bit occupied position and Diff to a remaining bit (S2315).

After that, the three-dimensional data encoding device encodes thecalculated 1-bit occupied position (S2305).

Next, the three-dimensional data encoding device calculates a remainingbit (S2306) and performs binary coding on the remaining bit (S2307).

Specifically, the three-dimensional data encoding device sets 1-bitoccupied position −1 to variable b (S2321). Then, the three-dimensionaldata encoding device sets remaining bit −2^(b) to variable Diff (S2322).After that, the three-dimensional data encoding device determineswhether Diff>−1 is satisfied (S2323).

When Diff>−1 is satisfied (YES in S2323), the three-dimensional dataencoding device encodes “1” and sets Diff to the remaining bit (S2324),and sets b−1 to variable b (S2326). On the other hand, when Diff>−1 isnot satisfied (NO in S2323), the three-dimensional data encoding deviceencodes “0” (S2325) and sets b−1 to variable b (S2326).

Finally, the three-dimensional data encoding device determines whetherb<0 is satisfied (S2327). When b<0 is not satisfied (NO in S2327), thethree-dimensional data encoding device performs step S2322 and thesubsequent steps again. When b<0 is satisfied (YES in S2327), thethree-dimensional data encoding device completes the process.

Hereinafter, a processing flow in the three-dimensional data decodingdevice will be described. FIG. 168 is a flowchart of a three-dimensionaldata decoding process performed by the three-dimensional data decodingdevice according to the present embodiment.

First, the three-dimensional data decoding device determines whether anoccupancy code of a parent node is a 1-bit occupied code (S2331). Whenthe occupancy code of the parent node is the 1-bit occupied code (YES inS2331), the three-dimensional data decoding device performs occupiedposition decoding for decoding encoded data encoded by occupied positionencoding (S2332).

Specifically, the three-dimensional data decoding device decodes a 1-bitoccupied position from a bitstream (S2334); calculates part of anoccupancy code (from the left end of the occupancy code to the 1-bitoccupied position), based on the 1-bit occupied position (S2335); andupdates the occupancy code while decoding a remaining bit (S2336).

On the other hand, when the occupancy code of the parent node is not the1-bit occupied code (NO in S2331), the three-dimensional data decodingdevice decodes the occupancy code from the bitstream using directdecoding for decoding an encoded occupancy code encoded by directencoding (S2333).

It should be noted that the order of the steps included in the occupiedposition decoding step (S2332) may be rearranged. For example, thethree-dimensional data decoding device may decode a 1-bit occupiedposition (S2334), then update an occupancy code while decoding aremaining bit (S2336), and finally add an occupancy code calculated fromthe 1-bit occupied position to the updated occupancy code (S2335);

FIG. 169 is a flowchart illustrating a specific example of the occupiedposition decoding step (S2332). First, the three-dimensional datadecoding device decodes a 1-bit occupied position from a bitstream(S2334) and calculates part of an occupancy code using the 1-bitoccupied position (S2335).

Specifically, the three-dimensional data decoding device sets the 1-bitoccupied position to variable a (S2341). Next, the three-dimensionaldata decoding device sets 2^(a) to an occupancy code (S2342).

Then, the three-dimensional data decoding device updates the occupancycode while decoding a remaining bit (S2336). Specifically, thethree-dimensional data decoding device sets a−1 to variable b (S2351).Next, the three-dimensional data decoding device decodes a 1 bit andsets the decoded 1 bit to variable c (S2352). Then, thethree-dimensional data decoding device determines whether c==1 issatisfied (S2353).

When c==1 is satisfied (YES in S2353), the three-dimensional datadecoding device adds 2^(b) to the occupancy code (S2354) and sets b−1 tovariable b (S2355). When c==1 is not satisfied (NO in S2353), thethree-dimensional data decoding device sets b−1 to variable b (S2355).

Finally, the three-dimensional data decoding device determines whetherb<0 is satisfied (S2356). When b<0 is not satisfied (NO in S2356), thethree-dimensional data decoding device performs step S2352 and thesubsequent steps again. When b<0 is satisfied (YES in S2356), thethree-dimensional data decoding device completes the process.

Next, a configuration example of the three-dimensional data encodingdevice will be described. FIG. 170 is a block diagram ofthree-dimensional data encoding device 2300 according to the presentembodiment. Three-dimensional data encoding device 2300 includes octreegenerator 2301 and entropy encoder 2302.

Octree generator 2301 generates, for example, an octree from inputtedthree-dimensional points (a point cloud), and generates a correspondingone of an occupancy code and leaf information for each node of theoctree.

Entropy encoder 2302 encodes the occupancy code of each node. Entropyencoder 2302 switches between occupancy code encoding methods accordingto whether an occupancy code of a parent node is a 1-bit occupied code.For example, when the occupancy code of the parent node is the 1-bitoccupied code, entropy encoder 2302 performs occupied position encodingon the occupancy code; and when the parent node is not the 1-bitoccupied code, entropy encoder 2302 performs arithmetic encoding on avalue of the occupancy code using a coding table.

Next, a configuration example of the three-dimensional data decodingdevice will be described. FIG. 171 is a block diagram ofthree-dimensional data decoding device 2310 according to the presentembodiment. Three-dimensional data decoding device 2310 includes octreegenerator 2311 and entropy decoder 2312.

Octree generator 2311 generates an octree of a space (a node) using, forexample, header information of a bitstream. For example, octreegenerator 2311 generates a large space (a root node) using the size of aspace along the x-axis, y-axis, and z-axis directions appended to theheader information, and generates an octree by generating eight smallspaces A (nodes A0 to A7) by dividing the space into two along each ofthe x-axis, y-axis, and z-axis directions. In a similar way, octreegenerator 2311 further divides each of nodes A0 to A7 into eight smallspaces. As stated above, octree generator 2311 repeats the generation ofan octree.

Entropy decoder 2312 decodes an occupancy code of each node. Entropydecoder 2312 switches between occupancy code decoding methods accordingto whether a decoded occupancy code of a parent node is a 1-bit occupiedcode. For example, when the decoded occupancy code of the parent node isthe 1-bit occupied code, entropy decoder 2312 decodes the occupancy codeusing occupied position decoding; and when the parent node is not the1-bit occupied code, entropy decoder 2312 performs arithmetic decodingon a value of the occupancy code using a coding table.

As stated above, the three-dimensional data encoding device according tothe present embodiment performs the process illustrated in FIG. 172.First, the three-dimensional data encoding device generates a bitsequence (e.g., an occupancy code) including N-bit information that isinformation of a current node included in an N-ary tree structure ofthree-dimensional points included in three-dimensional data and thatindicates whether a three-dimensional point is present in each of childnodes belonging to the current node, where N is an integer greater thanor equal to 2 (S2361).

Next, the three-dimensional data encoding device generates (i) positioninformation indicating a head position (e.g., a 1-bit occupied position)that is a position at which a predetermined code appears first in thebit sequence when the bit sequence is scanned in a predetermined scanorder, and (ii) a remaining bit that is part of the bit sequence afterthe head position in the predetermined scan order (S2362). Here, forexample, the predetermined code is 1.

Then, the three-dimensional data encoding device encodes the positioninformation and the remaining bit as information of the current node(S2363). In other words, the three-dimensional data encoding devicegenerates, as the information of the current node, a bitstream includingthe position information and the remaining bit.

Accordingly, the three-dimensional data encoding device can improve thecoding efficiency.

For example, the three-dimensional data encoding device has a first mode(e.g., occupied position encoding) for encoding the position informationand the remaining bit and a second mode (e.g., direct encoding) forencoding the bit sequence, and selects one of the first mode and thesecond mode based on whether a peripheral node of the current nodeincludes a three-dimensional point.

Accordingly, the three-dimensional data encoding device can improve thecoding efficiency by selecting a mode according to a state of theperipheral three-dimensional point.

For example, the three-dimensional data encoding device selects thefirst mode when a total number of peripheral nodes each including athree-dimensional point among peripheral nodes of the current node or aproportion of the peripheral nodes each including a three-dimensionalpoint to the peripheral nodes of the current node is less than apredetermined threshold value; and the three-dimensional data encodingdevice selects the second mode when the total number of the peripheralnodes or the proportion of the peripheral nodes is greater than thepredetermined threshold value.

For example, the three-dimensional data encoding device selects one ofthe first mode and the second mode based on a bit sequence of a parentnode of the current node.

For example, the three-dimensional data encoding device selects thefirst mode when a total number of child nodes each including athree-dimensional point among child nodes belonging to the parent nodeis less than a predetermined threshold value, the total number of thechild nodes being indicated by the bit sequence of the parent node; andthe three-dimensional data encoding device selects the second mode whenthe total number of the child nodes is greater than the predeterminedthreshold value.

For example, the three-dimensional data encoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

Moreover, the three-dimensional data decoding device according to thepresent embodiment performs the process illustrated in FIG. 173. First,the three-dimensional data decoding device decodes, from a bitstream,(i) position information indicating a head position (e.g., a 1-bitoccupied position) that is a position at which a predetermined codeappears first in a bit sequence (e.g., an occupancy code) when the bitsequence is scanned in a predetermined scan order, and (ii) a remainingbit that is part of the bit sequence after the head position in thepredetermined scan order, the bit sequence including N-bit informationthat is information of a current node included in an N-ary treestructure of three-dimensional points included in three-dimensional dataand that indicates whether a three-dimensional point is present in eachof child nodes belonging to the current node, where N is an integergreater than or equal to 2 (S2371). In other words, thethree-dimensional data decoding device obtains, from the bitstream, theposition information and the remaining bit. Additionally, for example,the predetermined code is 1.

Next, the three-dimensional data decoding device restores the bitsequence of the current node from the position information and theremaining bit (S2372), and restores the N-ary tree structure using thebit sequence (S2373). In other words, the three-dimensional datadecoding device restores position information of three-dimensionalpoints.

Accordingly, the three-dimensional data decoding device can improve thecoding efficiency.

For example, the three-dimensional data decoding device has a first mode(occupied position decoding) for decoding the position information andthe remaining bit and a second mode (direct decoding) for decoding thebit sequence, and selects one of the first mode and the second modebased on whether a peripheral node of the current node includes athree-dimensional point.

Accordingly, the three-dimensional data decoding device can improve thecoding efficiency by selecting a mode according to a state of theperipheral three-dimensional point.

For example, the three-dimensional data decoding device selects thefirst mode when a total number of peripheral nodes each including athree-dimensional point among peripheral nodes of the current node or aproportion of the peripheral nodes each including a three-dimensionalpoint to the peripheral nodes of the current node is less than apredetermined threshold value; and the three-dimensional data decodingdevice selects the second mode when the total number of the peripheralnodes or the proportion of the peripheral nodes is greater than thepredetermined threshold value.

For example, the three-dimensional data decoding device selects one ofthe first mode and the second mode based on a bit sequence of a parentnode of the current node.

For example, the three-dimensional data decoding device selects thefirst mode when a total number of child nodes each including athree-dimensional point among child nodes belonging to the parent nodeis less than a predetermined threshold value, the total number of thechild nodes being indicated by the bit sequence of the parent node; andthe three-dimensional data decoding device selects the second mode whenthe total number of the child nodes is greater than the predeterminedthreshold value.

For example, the three-dimensional data decoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

Embodiment 15

In the present embodiment, a three-dimensional data encoding deviceperforms quantization on three-dimensional position information of aninputted three-dimensional point cloud, and encodes thethree-dimensional position information using an octree structure. Atthis time, three-dimensional points (hereinafter referred to asduplicated points) occur that have the same three-dimensional positionbut have different attribute information such as a color or a degree ofreflection due to quantization. The three-dimensional data encodingdevice appends, to a header, information for controlling how to encodethese duplicated points as leaf information of an octree. As a result, athree-dimensional data decoding device can decode the leaf informationcorrectly. Here, the expression “have the same three-dimensionalposition . . . due to quantization” includes a state in which, as withpoint A and point B illustrated in FIG. 174, original three-dimensionalpositions are close to each other and values of the three-dimensionalpositions become identical due to quantization of information of thethree-dimensional positions.

For example, the three-dimensional data encoding device appends, toheader information, a merge duplicated point flag(MergeDuplicatedPointFlag) that is a flag for controlling whether tomerge duplicated points. FIG. 175 is a diagram schematicallyillustrating a process according to a merge duplicated point flag.

When the merge duplicated point flag is 1, the three-dimensional dataencoding device merges duplicated points into a point and encodes thepoint. Here, the term “merge” means, when, for example, point A andpoint B are duplicated points, keeping point A and removing point B orvice versa. It should be noted that, in such case, the three-dimensionaldata encoding device may calculate new attribute information from piecesof attribute information, such as a color or a degree of reflection, ofpoint A and point B; and may assign the calculated attribute informationto the merged point. For example, the three-dimensional data encodingdevice may assign an average value of the pieces of attributeinformation of point A and point B to the merged point.

Moreover, since each leaf when encoding is performed using the octreeincludes a single point when the merge duplicated point flag is 1, thethree-dimensional data encoding device need not encode, as leafinformation, information indicating how many three-dimensional pointsthe leaf includes. The three-dimensional data encoding device may alsoencode three-dimensional position information of the single point in theleaf, and information regarding attribute information such as a color ora degree of reflection.

As stated above, when duplicated points are unnecessary after decoding,the three-dimensional data encoding device sets a merge duplicated pointflag to 1, appends the merge duplicated point flag to a stream, mergesthe duplicated points, and encodes the merged point. Consequently, it ispossible to reduce a data mount of the unnecessary duplicated points,thereby increasing the coding efficiency.

When the merge duplicated point flag is 0, the three-dimensional dataencoding device encodes information of the duplicated points as leafinformation. For example, since each leaf may include one or moreduplicated points, the three-dimensional data encoding device encodesinformation indicating how many three-dimensional points the leafincludes. The three-dimensional data encoding device may also encodeattribute information of each of the duplicated points. For example,when point A and point Bare present as duplicated points in a leaf, thethree-dimensional data encoding device may encode information indicatingthat two points are present in the leaf. In addition, thethree-dimensional data encoding device may encode attribute informationof each of point A and point B.

As stated above, when duplicated points are necessary after decoding,the three-dimensional data encoding device sets a merge duplicated pointflag to 0, appends the merge duplicated point flag to a stream, andencodes the duplicated points. As a result, the three-dimensional datadecoding device can decode information regarding the duplicated pointscorrectly.

For example, as an example of quantization of a three-dimensionalposition, the three-dimensional data encoding device calculates aquantization position (x/qx, y/qy, z/qz) by dividing a three-dimensionalposition (x, y, z) by a quantization parameter (qx, qy, qz).

The merge duplicated point flag may be included in header information ofa bitstream. For example, the merge duplicated point flag may beincluded in the header of a bitstream such as WLD, SPC, or VLM.

It should be noted that although examples of the attribute informationinclude a color or a degree of reflection in the above description, theattribute information is not limited to this. For example, the attributeinformation may include a normal vector of a point, informationindicating a degree of importance of a point, a three-dimensionalfeature of a point, or position information such as a latitude, alongitude, and an altitude of a point.

The term “merge” represents combining two or more points into a point.In addition, the term “merge” may represent combining M or more pointsinto N points, where M>N.

As stated above, duplicated points occur that have the same coordinatesas a three-dimensional point cloud but has different attributeinformation such as a color or a degree of reflection due toquantization. For example, although point A and point B have differentthree-dimensional positions before quantization, there occurs a case inwhich point A and point B come to have the same three-dimensionalposition but have different attribute information due to quantization.In short, point A and point B are duplicated points.

It should be noted that the above case is not limited to quantization,and there is also a case in which duplicated points are caused to occurby a sensor such as LiDAR obtaining three-dimensional positions andattribute information of a point cloud of the same object at differenttimes or in different directions.

The expression “have the same three-dimensional position” is not limitedto a case in which three-dimensional positions are completely the same.For example, when a difference between three-dimensional positions ofpoint A and point B is less than or equal to threshold value a, thethree-dimensional data encoding device may regard point A and point B ashaving the same three-dimensional position and determine that point Aand point B are duplicated points. In addition, the three-dimensionaldata encoding device may add threshold value a to a stream and notifythe three-dimensional data decoding device that any point less than orequal to threshold value a has been handled as a duplicated point.

Moreover, the three-dimensional data encoding device may use thethree-dimensional position of point A as a three-dimensional position ofa duplicated point. Alternatively, the three-dimensional data encodingdevice may use the three-dimensional position of point B as athree-dimensional position of a duplicated point. Alternatively, thethree-dimensional data encoding device may use, as a three-dimensionalposition of a duplicated point, a three-dimensional position calculatedfrom the three-dimensional position of point A and the three-dimensionalposition of point B. For example, the three-dimensional data encodingdevice may use an average value between the three-dimensional positionof point A and the three-dimensional position of point B.

The three-dimensional data encoding device may merge, among duplicatedpoints, points having the same three-dimensional position and the sameattribute information or may delete one of the points regardless of avalue of a merge duplicated point flag.

When a merge duplicated point flag is 1, the three-dimensional dataencoding device may merge M points in a leaf into N points, where M>N.In this case, the three-dimensional data encoding device may encode, asleaf information, each of pieces of three-dimensional positioninformation and pieces of attribute information of N points. Inaddition, the three-dimensional data encoding device may calculate Npieces of attribute information using M pieces of attribute information.

The three-dimensional data encoding device may add the number of points(N) in a leaf after merging to a header and notify the number of thepoints (N) to the three-dimensional data decoding device. A value of Nmay be set in advance as a fixed value by standards etc. This eliminatesthe need for adding information indicating N for each leaf, and it isthus possible to reduce a generated coding amount. Accordingly, thethree-dimensional data decoding device can decode N points correctly.

When a merge duplicated point flag is 1, duplicated points are mergedinto a point. For example, the three-dimensional data encoding devicemay merge point A and point B into point C having the samethree-dimensional position information as point A and point B. It shouldbe noted that the three-dimensional data encoding device may assign, topoint C, an average value of pieces of attribute information, such as acolor or a degree of reflection, of point A and point B. Additionally,the three-dimensional data encoding device may merge point B with pointA or merge point A with point B.

Next, an example of a syntax of a merge duplicated point flag will bedescribed. FIG. 176 is a diagram illustrating an example of a syntax ofheader information. FIG. 177 is a diagram illustrating an example of asyntax of information of a node.

As illustrated in FIG. 176, the header information includes a mergeduplicated point flag (MergeDuplicatedPointFlag). The merge duplicatedpoint flag is information indicating whether to merge duplicated points.For example, a value of 1 of the merge duplicated point flag indicatesthat duplicated points are to be merged, and a value of 0 of the mergeduplicated point flag indicates that duplicated points are not to bemerged.

It should be noted that the three-dimensional data encoding device mayspecify whether to merge duplicated points, based on standards or aprofile or level, etc. of standards, without appending a mergeduplicated point flag to a header. This enables the three-dimensionaldata decoding device to determine whether a stream includes a duplicatedpoint by reference to standards information, and to restore a bitstreamcorrectly.

As illustrated in FIG. 177, the information of the node includes isleafand num_point_per_leaf. isleaf is a flag indicating whether a currentnode is a leaf. A value of 1 indicates that a current node is a leaf,and a value of 0 indicates that a current node is not a leaf but a node.It should be noted that information indicating whether a node is a leafneed not be appended to a header. In this case, the three-dimensionaldata decoding device determines whether a node is a leaf using anothermethod. For example, the three-dimensional data decoding device maydetermine whether each node of an octree is divided into the smallestpossible size, and may determine that a node is a leaf when determiningthat each node is divided into the smallest possible size. Thiseliminates the need for encoding the flag indicating whether the node isthe leaf, which makes it possible to reduce the code amount of theheader.

num_point_per_leaf is leaf information and indicates the number ofthree-dimensional points included in a leaf. When a merge duplicatedpoint flag is 0, num_point_per_leaf is encoded. Additionally, since thenumber of points in a leaf is 1 when a merge duplicated point flag is 1,num_point_per_leaf is not encoded. Accordingly, it is possible to reducethe code amount.

It should be noted that although whether to encode leaf information isselected directly according to a merge duplicated point flag in theexample described here, whether to encode leaf information may beselected indirectly. For example, the three-dimensional data encodingdevice may change single_point_per_leaf illustrated in FIG. 156according to a merge duplicated point flag, and select whether to encodeleaf information, based on the syntax illustrated in FIG. 156. In otherwords, when the merge duplicated point flag is 1, the three-dimensionaldata encoding device may set single_point_per_leaf to 1; and when themerge duplicated point flag is 0, the three-dimensional data encodingdevice may set single_point_per_leaf to 0. In this case, thethree-dimensional data encoding device also need not append the mergeduplicated point flag to a bitstream.

The three-dimensional data encoding device may entropy encodenum_point_per_leaf. At this time, the three-dimensional data encodingdevice may also perform encoding while switching coding tables. Forexample, the three-dimensional data encoding device may performarithmetic encoding on the first bit using coding table A. and mayperform arithmetic encoding on a remaining bit using coding table B.

As stated above, the three-dimensional data encoding device appends, tothe header of a bitstream, information indicating whether to mergeduplicated points, and selects whether to merge the duplicated pointsaccording to the value. When merging the duplicated points, thethree-dimensional data encoding device need not encode, as leafinformation, the number of points included in a leaf. When not mergingthe duplicated points, the three-dimensional data encoding device mayencode, as leaf information, the number of points included in a leaf.

The three-dimensional data encoding device may also entropy encodeisleaf, MergeDuplicatedPointFlag, and num_point_per_leaf generated bythe above method. For example, the three-dimensional data encodingdevice may binarize each value and perform arithmetic encoding on thevalue.

Although the octree structure has been described as an example in thepresent embodiment, the present disclosure is not necessarily limited tothis. The aforementioned procedure may be applied to an N-ary tree suchas the quadtree and the hexadecatree, or other tree structures, where Nis an integer greater than or equal to 2.

When encoding is performed with a merge duplicated point flag=1, and anoriginal inputted three-dimensional point cloud or quantizedthree-dimensional point cloud includes duplicated points, lossy codingis used, and it is thus possible to reduce the code amount. Besides,when the original inputted three-dimensional point cloud includes noduplicated point and encoding is performed using lossless coding(encoding is performed while skipping quantization), thethree-dimensional data encoding device may perform encoding with themerge duplicated point flag=1. Accordingly, it is possible to reduce acode amount by as much as a code amount resulting from not encodingnum_point_per_leaf while maintaining lossless coding.

Moreover, when the three-dimensional data encoding device encodes, asleaf information, each of two or more duplicated points in the sameleaf, the three-dimensional data encoding device may also encode each ofpieces of attribute information (e.g., a color or a degree ofreflection) of the respective points. In this case, the pieces ofattribute information of the respective points may be associated in acoding order of the points. For example, when the three-dimensional dataencoding device encodes each of points A and B in the same leaf as leafinformation, the three-dimensional data encoding device may encodepieces of attribute information of both points A and B and append thepieces of attribute information to a bitstream. Additionally, the piecesof attribute information may be associated in a coding order of points Aand B. For example, when each three-dimensional position is encoded inorder from point A to point B, it is conceivable that the pieces ofattribute information are encoded in order from point A to point B andare associated.

Moreover, when the three-dimensional data encoding device merges M ormore point clouds in the same leaf and encodes the merged point cloudsas N points, where M>N, the three-dimensional data encoding device mayround off M or more pieces of attribute information of M or more pointclouds by, for example, averaging to generate pieces of attributeinformation of N points, and may encode the pieces of attributeinformation. For example, when the three-dimensional data encodingdevice merges points A and B in the same leaf into a point and encodesthe point, the three-dimensional data encoding device may round offpieces of attribute information of points A and B by, for example,averaging to calculate attribute information of the point, and mayencode the calculated attribute information.

Moreover, the three-dimensional data encoding device may change a methodof calculating attribute information according to a degree of importanceor feature of a point. For example, the three-dimensional data encodingdevice may give a high weight to attribute information of a point havinga high degree of importance or a point having a great feature, calculatea weighted average value, and use the calculated value as attributeinformation after merging. In addition, the three-dimensional dataencoding device may change a weight according to a difference betweenthree-dimensional positions before and after quantization. For example,a higher weight may be given as the difference is smaller, a weightedaverage value may be calculated, and the calculated value may be used asattribute information after merging.

Next, a procedure for a three-dimensional data encoding processperformed by the three-dimensional data encoding device will bedescribed. FIG. 178 and FIG. 179 each are a flowchart of athree-dimensional data encoding process performed by thethree-dimensional data encoding device.

First, the three-dimensional data encoding device determines whether tomerge duplicated points and perform encoding (S2401). For example, whenthe three-dimensional data encoding device prioritizes the codingefficiency, the three-dimensional data encoding device may determine tomerge duplicated points. When duplicated points are necessary in thethree-dimensional data decoding device, the three-dimensional dataencoding device may also determine not to merge the duplicated points.Moreover, when an inputted three-dimensional point cloud includes noduplicated point, and no lossless coding, that is, no quantization isperformed, the three-dimensional data encoding device may set a mergeduplicated point flag to I. Since this prevents the number of points ina leaf from being encoded as leaf information, it is possible to reducethe code amount.

When the three-dimensional data encoding device merges the duplicatedpoints and performs encoding (YES in S2401), the three-dimensional dataencoding device sets a merge duplicated point flag to I and appends themerge duplicated point flag to a header (S2402).

When the three-dimensional data encoding device neither merges theduplicated points nor performs encoding (NO in S2401), thethree-dimensional data encoding device sets a merge duplicated pointflag to 0 and appends the merge duplicated point flag to a header(S2403).

Next, the three-dimensional data encoding device quantizesthree-dimensional positions of an inputted three-dimensional point cloud(S2404). As an example of quantization of a three-dimensional position,the three-dimensional data encoding device calculates a quantizationposition (x/qx, y/qy, z/qz) by dividing a three-dimensional position (x,y, z) by a quantization parameter (qx, qy, qz). Additionally, thethree-dimensional data encoding device may append the quantizationparameter to the header, and the three-dimensional data decoding devicemay perform inverse quantization using the quantization parameter. Itshould be noted that the three-dimensional data encoding device may skipquantization at the time of lossless coding.

Then, the three-dimensional data encoding device determines whether themerge duplicated point flag is 1 (S2405). When the merge duplicatedpoint flag is 1 (YES in S2405), the three-dimensional data encodingdevice merges duplicated points of the quantized three-dimensional pointcloud (S2406). It should be noted that when lossless coding is performedand the inputted three-dimensional point cloud includes no duplicatedpoint, the three-dimensional data encoding device may skip this step.

When the merge duplicated point flag is 0 (NO in S2405), thethree-dimensional data encoding device merges no duplicated points.

After that, the three-dimensional data encoding device divides a nodeinto an octree (S2411). For example, the three-dimensional data encodingdevice may calculate an occupancy code of each node of an octreesequentially while performing octree division initially on a large space(a root node) including a quantized three-dimensional point cloud, andmay encode the calculated occupancy code. In addition, thethree-dimensional data encoding device may perform octree divisionrepeatedly and encode leaf information when octree division cannot beperformed. It should be noted that the three-dimensional data encodingdevice may calculate occupancy codes and pieces of leaf information ofall nodes in advance, and then encode these pieces of information.

Next, the three-dimensional data encoding device determines whether thenext node (a current node) is a leaf (S2412). For example, thethree-dimensional data encoding device may determine whether an octreeis divided into the smallest possible size, and may determine that anode is a leaf when determining that the octree is divided into thesmallest possible size.

When the current node is the leaf (YES in S2412), the three-dimensionaldata encoding device determines whether a merge duplicated point flag is0 (S2413). When the merge duplicated point flag is 0 (YES in S2413), thethree-dimensional data encoding device encodes the number ofthree-dimensional points included in the leaf (num_point_per_leaf)(S2414). When the merge duplicated point flag is 1 (NO in S2413), thethree-dimensional data encoding device does not encode the number ofthree-dimensional points included in the leaf (num_point_per_leaf).

Moreover, when the current node is not the leaf (NO in S2412), thethree-dimensional data encoding device encodes an occupancy code of thecurrent node (S2415).

Then, the three-dimensional data encoding device determines whetherprocessing of all the nodes is completed (S2416). When the processing ofall the nodes is not completed (NO in S2416), the three-dimensional dataencoding device performs step S2412 and the subsequent steps on the nextnode.

When the processing of all the nodes is completed (YES in S2416), thethree-dimensional data encoding device encodes attribute informationregarding the encoded three-dimensional points (S2417).

It should be noted that the three-dimensional data encoding device mayadjust the size of the large space (the root node) along the x-axis,y-axis, or z-axis to a power-of-two size so that the large space can bealways divided equally into two with respect to each axis. Besides, thethree-dimensional data encoding device may adjust the size of the largespace so that a divided node always becomes a cube. For example, whenthree-dimensional positions of three-dimensional point clouds take avalue from 0 to 256 along the x-axis, a value from 0 to 120 along they-axis, and a value from 0 to 62 along the z-axis, first, thethree-dimensional data encoding device compares the minimum value andthe maximum value of each axis and calculates the minimum value and themaximum value of coordinates of all the point clouds. In this case, theminimum value is 0, and the maximum value is 256. Next, thethree-dimensional data encoding device calculates values that includethe calculated minimum value and maximum value and enable the largespace to have the power-of-two size. In this case, the size is 512, andthe minimum value and maximum value of the coordinates in the space are0 and 511, respectively. As a result, it is possible to include pointclouds in a range of 0 to 256. In this case, the three-dimensional dataencoding device also starts octree division initially on a large spacehaving a size of 512×512×512.

Next, a procedure for a three-dimensional data decoding processperformed by the three-dimensional data decoding device will bedescribed. FIG. 180 is a flowchart of a three-dimensional data decodingprocess performed by the three-dimensional data decoding device. First,the three-dimensional data decoding device decodes a merge duplicatedpoint flag in the header of a bitstream (52421).

Next, the three-dimensional data decoding device divides a node into anoctree (S2422). For example, the three-dimensional data decoding devicegenerates an octree of a space (a node) using header information etc. ofa bitstream. For example, the three-dimensional data decoding devicegenerates a large space (a root node) using the size of a space alongthe x-axis, y-axis, and z-axis directions appended to the headerinformation, and generates an octree by generating eight small spaces A(nodes A0 to A7) by dividing the space into two along each of thex-axis, y-axis, and z-axis directions. In a similar way, thethree-dimensional data decoding device further divides each of nodes A0to A7 into eight small spaces. As stated above, the three-dimensionaldata decoding device performs decoding of an occupancy code of each nodeand decoding of leaf information in sequence through the above-mentionedprocess.

Then, the three-dimensional data decoding device determines whether thenext node (a current node) is a leaf (S2423). When the current node isthe leaf (YES in S2423), the three-dimensional data decoding devicedetermines whether a merge duplicated point flag is 0 (S2424). When themerge duplicated point flag is 0 (YES in S2424), the three-dimensionaldata decoding device decodes the number of three-dimensional pointsincluded in the leaf (num_point_per_leaf) from the bitstream (S2425). Onthe other hand, when the merge duplicated point flag is 1 (NO in S2424),the three-dimensional data decoding device does not decode the number ofthree-dimensional points included in the leaf (num_point_per_leaf) fromthe bitstream.

Moreover, when the next node is not the leaf (NO in S2423), thethree-dimensional data decoding device decodes an occupancy code of thecurrent node from the bitstream (S2426).

After that, the three-dimensional data decoding device calculatesthree-dimensional positions of leaves using the decoded occupancy codeand information about the number of times octree division is performedetc (S2427). For example, when the large space has a size of 8×8×8,performing octree division three times causes a node to have a size of1×1×1. This size (1×1×1) is the smallest divisible unit (leaf).Additionally, the three-dimensional data decoding device determineswhether each leaf includes a point, based on a decoded occupancy code ofa parent node of the leaf. Accordingly, the three-dimensional datadecoding device can calculate a three-dimensional position of each leaf.

Next, the three-dimensional data decoding device inverse quantizes thecalculated three-dimensional positions (S2428). Specifically, thethree-dimensional data decoding device calculates three-dimensionalpositions of a point cloud by performing inverse quantization using aquantization parameter decoded from the header. For example, as anexample of inverse quantization of a three-dimensional position, thethree-dimensional data decoding device calculates an inversequantization position (xxqx, yxqy, zxqz) by multiplying athree-dimensional position (x, y, z) prior to inverse quantization by aquantization parameter (qx, qy, qz). It should be noted that thethree-dimensional data decoding device may skip inverse quantization atthe time of lossless coding. In addition, when a scale need not bereturned to an original scale, the three-dimensional data decodingdevice may skip inverse quantization even at the time of no losslesscoding (lossy coding). For example, when not an absolute positionalrelationship between three-dimensional points but a relative positionalrelationship between three-dimensional points is necessary, thethree-dimensional data decoding device may skip inverse quantization.

Then, the three-dimensional data decoding device determines whetherprocessing of all the nodes is completed (S2429). When the processing ofall the nodes is not completed (NO in S2429), the three-dimensional datadecoding device performs step S2423 and the subsequent steps on the nextnode.

When the processing of all the nodes is completed (YES in S2429), thethree-dimensional data decoding device finally decodes attributeinformation regarding the decoded three-dimensional points from thebitstream (S2430). It should be noted that when the merge duplicatedpoint flag is 1, attribute information is associated with each pointhaving a different decoded three-dimensional position after thedecoding. Also, when the merge duplicated point flag is 0, differentpieces of attribute information are decoded and associated with pointshaving the same decoded three-dimensional position.

Next, a configuration example of the three-dimensional data encodingdevice will be described. FIG. 181 is a block diagram ofthree-dimensional data encoding device 2400 according to the presentembodiment. Three-dimensional data encoding device 2400 includesquantizer 2401, octree generator 2402, merge determiner 2403, andentropy encoder 2404.

Quantizer 2401 quantizes inputted three-dimensional points (a pointcloud). It should be noted that in the event of lossless coding,quantization may be skipped.

Octree generator 2402 generates, for example, an octree from theinputted three-dimensional points (the point cloud), and generates acorresponding one of an occupancy code and leaf information for eachnode of the octree.

Merge determiner 2403 determines whether to merge duplicated points andperform encoding, and sets a value of a merge duplicated point flag,based on a result of the determination. For example, merge determiner2403 determines the value of the merge duplicated point flag usinginformation of a quantized three-dimensional point cloud. For example,merge determiner 2403 determines the value of the merge duplicated pointflag, based on whether the quantized three-dimensional point cloudincludes duplicated points.

Entropy encoder 2404 generates a bitstream by encoding the leafinformation according to the merge duplicated point flag. Entropyencoder 2404 may append the merge duplicated point flag to thebitstream. Moreover, entropy encoder 2404 may encode the occupancy code.Furthermore, entropy encoder 2404 may encode attribute informationregarding encoded three-dimensional points.

Next, a configuration example of the three-dimensional data decodingdevice will be described. FIG. 182 is a block diagram ofthree-dimensional data decoding device 2410 according to the presentembodiment. Three-dimensional data decoding device 2410 includes octreegenerator 2411, merge information decoder 2412, entropy decoder 2413,and inverse quantizer 2414.

Octree generator 2411 generates an octree of a space (a node) using, forexample, header information of a bitstream. For example, octreegenerator 2411 generates a large space (a root node) using the size of aspace along the x-axis, y-axis, and z-axis directions appended to theheader information, and generates an octree by generating eight smallspaces A (nodes A0 to A7) by dividing the space into two along each ofthe x-axis, y-axis, and z-axis directions. In a similar way, octreegenerator 2411 further divides each of nodes A0 to A7 into eight smallspaces. As stated above, octree generator 2411 repeats the generation ofan octree.

Merge information decoder 2412 decodes a merge duplicated point flagfrom the header information of the bitstream. It should be noted thatmerge information decoder 2412 may be included in entropy decoder 2413.

Entropy decoder 2413 decodes leaf information according to informationof the decoded merge duplicated point flag, and generates athree-dimensional point cloud (three-dimensional positions). It shouldbe noted that entropy decoder 2413 may decode attribute informationregarding decoded three-dimensional points.

Inverse quantizer 2414 performs inverse quantization on thethree-dimensional positions of the decoded point cloud, and generates anoutput three-dimensional point cloud. It should be noted that in theevent of lossless coding, inverse quantization may be skipped. Inaddition, when a scale need not be returned to an original scale, thethree-dimensional data decoding device may skip inverse quantizationeven in the event of lossy coding. For example, when not an absolutepositional relationship between three-dimensional points but a relativepositional relationship between three-dimensional points is necessary,the three-dimensional data decoding device may skip inversequantization.

Next, a variation of the three-dimensional data encoding processperformed by the three-dimensional data encoding device will bedescribed. FIG. 183 is a flowchart of a variation of thethree-dimensional data encoding process.

First, the three-dimensional data encoding device quantizesthree-dimensional positions of an inputted three-dimensional point cloud(S2441). For example, as an example of quantization of athree-dimensional position, the three-dimensional data encoding devicecalculates a quantization position (x/qx, y/qy, z/qz) by dividing athree-dimensional position (x, y, z) by a quantization parameter (qx,qy, qz). Additionally, the three-dimensional data encoding device mayappend the quantization parameter to a header, and the three-dimensionaldata decoding device may perform inverse quantization using thequantization parameter. It should be noted that the three-dimensionaldata encoding device may skip quantization at the time of losslesscoding.

Next, the three-dimensional data encoding device determines whether thequantized three-dimensional point cloud includes duplicated points(S2442). For example, the three-dimensional data encoding devicecompares pieces of three-dimensional position information of allthree-dimensional point clouds, and makes the determination, based onwhether there is the same value. Alternatively, the three-dimensionaldata encoding device may calculate a difference between all the piecesof three-dimensional position information, and determine that thequantized three-dimensional point cloud includes no duplicated pointwhen an absolute value of the difference is greater than a predeterminedthreshold value.

When the three-dimensional point cloud includes the duplicated points(YES in S2442), the three-dimensional data encoding device determineswhether to merge the duplicated points and perform encoding (S2443). Forexample, when the three-dimensional data encoding device prioritizes thecoding efficiency, the three-dimensional data encoding device maydetermine to merge duplicated points. When duplicated points arenecessary in the three-dimensional data decoding device, thethree-dimensional data encoding device may also determine not to mergeduplicated points.

When the three-dimensional point cloud includes no duplicated point (NOin S2442) or the duplicated points are to be merged (YES in S2443), thethree-dimensional data encoding device sets a merge duplicated pointflag to I and appends the merge duplicated point flag to a header(S2444). In contrast, when the duplicated points are not to be merged(NO in S2443), the three-dimensional data encoding device sets a mergeduplicated point flag to 0 and appends the merge duplicated point flagto a header (2445).

After that, the three-dimensional data encoding device determineswhether the merge duplicated point flag is 1 (S2446). When the mergeduplicated point flag is 1 (YES in S2446), the three-dimensional dataencoding device merges duplicated points of the quantizedthree-dimensional point cloud (S2447). It should be noted that whenlossless coding is performed and the inputted three-dimensional pointcloud includes no duplicated point, the three-dimensional data encodingdevice may skip this step. When the merge duplicated point flag is 0 (NOin S2446), the three-dimensional data encoding device does not mergeduplicated points of the quantized three-dimensional point cloud.Subsequent steps are the same as those illustrated in FIG. 179.

As stated above, when a leaf included in an N-ary tree structure ofthree-dimensional points included in three-dimensional data includes twothree-dimensional points, and a difference between three-dimensionalpositions of the two three-dimensional points is less than apredetermined threshold value, where N is an integer greater than orequal to 2, the three-dimensional data encoding device according to thepresent embodiment appends, to a bitstream, first information (e.g., amerge duplicated point flag) indicating whether to merge the twothree-dimensional points; when the first information indicates that thetwo three-dimensional points are to be merged, the three-dimensionaldata encoding device merges the two three-dimensional points and encodesa merged three-dimensional point; and when the first informationindicates that the two three-dimensional points are not to be merged,the three-dimensional data encoding device encodes each of the twothree-dimensional points.

According to this configuration, the three-dimensional data encodingdevice can not only select whether to merge three-dimensional points butalso notify the three-dimensional data decoding device whetherthree-dimensional points are merged.

For example, when the first information indicates that the twothree-dimensional points are not to be merged, the three-dimensionaldata encoding device appends second information regarding the leaf(e.g., leaf information) to the bitstream; and when the firstinformation indicates that the two three-dimensional points are to bemerged, the three-dimensional data encoding device appends no leafinformation to the bitstream.

For example, the second information indicates the number ofthree-dimensional points included in the leaf.

For example, the three-dimensional data encoding device quantizesthree-dimensional positions of inputted three-dimensional points togenerate three-dimensional positions of the three-dimensional points.

For example, the three-dimensional data encoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

When a leaf included in an N-ary tree structure of three-dimensionalpoints included in three-dimensional data includes two three-dimensionalpoints, and a difference between three-dimensional positions of the twothree-dimensional points is less than a predetermined threshold value,where N is an integer greater than or equal to 2, the three-dimensionaldata decoding device according to the present embodiment decodes, from abitstream, first information (e.g., a merge duplicated point flag)indicating whether the two three-dimensional points are merged; when thefirst information indicates that the two three-dimensional points arenot merged, the three-dimensional data decoding device decodes secondinformation regarding the leaf (e.g., leaf information) from thebitstream; and when the first information indicates that the twothree-dimensional points are merged, the three-dimensional data decodingdevice decodes no leaf information from the bitstream.

For example, the second information indicates the number ofthree-dimensional points included in the leaf.

For example, the three-dimensional data decoding device restoresthree-dimensional positions of the three-dimensional points using theleaf information, and inverse quantizes the restored three-dimensionalpositions.

For example, the three-dimensional data decoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

It should be noted that the methods of the present embodiment may beapplied even when duplicated points and non-duplicated points arepresent in a quantized leaf. FIG. 184 is a diagram for illustrating thisprocess. For example, as illustrated in FIG. 184, point A, point B, andpoint D are present in a leaf in a state prior to quantization.Quantization causes point A and point B to have the samethree-dimensional position, and point A and point B become duplicatedpoints. In contrast, since point D has a different three-dimensionalposition from the other points, point D does not become a duplicatedpoint. Such a case occurs when octree division is not performed up tothe smallest unit of division and a node in processing is encoded as aleaf.

In such a case, when a merge duplicated point flag(MergeDuplicatedPointFlag) is 0, the three-dimensional data encodingdevice encodes information indicating how many point clouds each leafincludes, position information of each point cloud, and attributeinformation of each point cloud. Here, position information may beabsolute coordinates relative to a reference position of each pointcloud or may include relative coordinates of points included in a leafas described above. For example, the three-dimensional data encodingdevice may encode information indicating that a leaf includes point A,point B, and point D, position information of each of the points, andattribute information of each of the points.

Moreover, when a merge duplicated point flag is 1, the three-dimensionaldata encoding device merges duplicated points in a leaf. For example,the three-dimensional data encoding device merges point A and point Band encodes position information and attribute information after themerging. At this time, since point D is not merged, thethree-dimensional data encoding device encodes position information andattribute information of point D separately.

Furthermore, the three-dimensional data encoding device may encodeinformation indicating the number of points included in a leaf aftermerging. In an example illustrated in FIG. 184, since thethree-dimensional data encoding device merges point A and point B into apoint but does not merge point D, the three-dimensional data encodingdevice encodes the number of points included in the leaf as 2.

When a merge duplicated point flag is 1, the three-dimensional dataencoding device may merge M duplicated points in a leaf into N points,where M>N. In this case, the three-dimensional data encoding device mayencode, as leaf information, each of pieces of three-dimensionalposition information and attribute information of N points and each ofpieces of position information and attribute information of non-mergedpoints. In addition, the three-dimensional data encoding device maycalculate N pieces of attribute information using M pieces of attributeinformation.

Furthermore, the three-dimensional data encoding device may encodeinformation indicating the number of points included in a leaf. In theexample illustrated in FIG. 184, the three-dimensional data encodingdevice may encode information indicating the number of points includedin a leaf as 3. Additionally, the three-dimensional data encoding devicemay encode pieces of position information and attribute information ofall points.

Embodiment 16

In the present embodiment, a three-dimensional data encoding deviceobtains information of neighboring nodes each having a different parentnode, by searching encoded nodes. FIG. 185 is a diagram illustrating anexample of neighboring nodes. In the example illustrated in FIG. 185,three neighboring nodes belong to the same parent node as a currentnode. The three-dimensional data encoding device obtains neighboringinformation of these three neighboring nodes by checking an occupancycode of the parent node.

Three remaining neighboring nodes each belong to a parent node differentfrom the parent node of the current node. The three-dimensional dataencoding device obtains neighboring information of these threeneighboring nodes by checking information of encoded nodes. Here,neighboring information includes information indicating whether a nodeincludes a point cloud (is occupied). In addition, an encoded node is,for example, a node belonging to the same layer as a current node in anoctree:

FIG. 186 is a diagram illustrating an example of nodes to be searched.The three-dimensional data encoding device searches a search rangeincluding the encoded nodes illustrated in FIG. 186 for information of aneighboring node. FIG. 187 is a diagram for illustrating a searchprocess for a neighboring node. As illustrated in FIG. 187, informationof encoded nodes is stored in a queue. The three-dimensional dataencoding device obtains information of a neighboring node by searchingthe queue from its head. For example, a search order for a queue is acoding order.

The three-dimensional data encoding device calculates an occupancy codeof a current node by calculating information indicating whether childnodes are occupied. At this time, the three-dimensional data encodingdevice updates neighboring information of each child node. For example,the three-dimensional data encoding device determines whether aneighboring node having the same parent node as the current node isoccupied, based on an occupancy code. Moreover, the three-dimensionaldata encoding device searches a queue that stores encoded nodeinformation for information indicating whether a neighboring node havinga parent node different from the parent node of the current node isoccupied, and determines whether the neighboring node having the parentnode different from the parent node of the current node is occupied,based on the searched information. Furthermore, the three-dimensionaldata encoding device updates neighboring information of each child node,and stores the updated neighboring information into the queue tocalculate a neighboring node of a child node for the next node.

In each searching, the three-dimensional data encoding device updatesneighboring information of both a current node and a searched node. FIG.188 and FIG. 189 each are a diagram for illustrating this updateprocess. As illustrated in FIG. 188, in each searching, thethree-dimensional data encoding device updates neighboring informationof both a current node and a searched node. In other words, theneighboring information is transmitted in both directions. That thesearched node is a neighboring node is added to information of thecurrent node, and that the current node is a neighboring node is addedto information of a neighboring node.

As illustrated in FIG. 189, in a search process, an immediatelypreceding current node can become a searched node. In this case,neighboring information of the immediately preceding current node isupdated.

In order to ensure the longest processing time for hardwareimplementation, the three-dimensional data encoding device may completea search process before a neighboring node is found. FIG. 190 is adiagram for illustrating this operation.

As illustrated in FIG. 190, a search threshold value is predeterminedthat is a threshold value for stopping a search. This search thresholdvalue indicates, for example, the number of searches performed on aqueue from its head.

In an example illustrated in (1) of FIG. 190, a greater number of searchsteps than a search threshold value is required to search a queue forinformation of a neighboring node. In this example, thethree-dimensional data encoding device performs a search up to thesearch threshold value and completes the search process.

In an example illustrated in (2) of FIG. 190, it is possible to search aqueue for a neighboring node with a fewer number of search steps thanthe search threshold value. In this example, the three-dimensional dataencoding device searches for the neighboring node and completes thesearch process.

As stated above, the three-dimensional data encoding device may providea parameter (a search threshold value) for limiting the number ofsearches. By limiting the number of searches, it is possible to find aneighboring node while keeping a processing time for searching within acertain time. Additionally, the three-dimensional data encoding devicemay append, to the header etc. of a bitstream, information indicating alimiting value (a search threshold value) for the number of searches.Alternatively, the number of searches may be specified by standards etc.Accordingly, since a three-dimensional data decoding device candetermine a limiting value for the number of searches from a header orrequirements of standards, the three-dimensional data decoding devicecan decode a stream correctly.

Next, a specific example of a structure of a queue of encoded nodes willbe described. In order to identify a neighborhood of a current node,each element of a queue of encoded nodes has an index in athree-dimensional space. Examples of this index include a Morton code;

FIG. 191 is a diagram illustrating an example of indexes for whichMorton codes are used. FIG. 192 is a diagram illustrating an example ofa queue for which Morton codes are used. In the example illustrated inFIG. 191, the current node has an index of 3, the left node has an indexof 2, and the lower node has an index of 1. It is possible to determinea neighboring node using the Morton codes as the indexes in the abovemanner.

The use of Morton codes produces the following effects. The first effectmakes it possible to speed up a search process. Here, a search processin which x, y, z coordinates are used is more complex than a process offinding a Morton code that is a single integer.

The second effect makes it possible to reduce an amount of data to beheld, by using Morton codes. Specifically, when x, y, z coordinates areused, three 32-bit data are required. In contrast, a node can beidentified by one 64-bit data, by using Morton codes.

It should be noted that any method other than Morton codes may be usedas a method of converting a three-dimensional position into an integer.For example, space-filling curve capable of converting athree-dimensional position into an integer, such as Hilbert curve, maybe used.

Next, a configuration example of the three-dimensional data encodingdevice according to the present embodiment will be described. FIG. 193is a block diagram of three-dimensional data encoding device 2500according to the present embodiment. Three-dimensional data encodingdevice 2500 includes octree generator 2501, parent node informationobtainer 2502, encoding mode selector 2503, searcher 2504, geometryinformation calculator 2505, coding table selector 2506, and entropyencoder 2507.

Octree generator 2501 generates, for example, an octree from inputtedthree-dimensional points (a point cloud), and generates an occupancycode for each node of the octree.

Parent node information obtainer 2502 obtains neighboring information ofa neighboring node from an occupancy code of a parent node of a currentnode. In other words, parent node information obtainer 2502 obtains, forexample, neighboring information of neighboring nodes that are, amongneighboring nodes, neighboring nodes belonging to the same parent nodeas the current node and account for half of the neighboring nodes.

Encoding mode selector 2503 selects an encoding mode (a coding mode).For example, this encoding mode includes a mode for performing one of asearch process and a process of obtaining neighboring information froman occupancy code of a parent node, and a mode for performing the both.

Searcher 2504 obtains neighboring information of a neighboring nodethrough a search process, using information of encoded nodes. Althoughthis search process requires some processing time, the search processmakes it possible to obtain neighboring information of all neighboringnodes.

Geometry information calculator 2505 generates neighboring information(occupancy information of a neighboring node) to be used for selecting acoding table, by using one of the neighboring information obtained byparent node information obtainer 2502 and the neighboring informationobtained by searcher 2504, or by integrating the both.

Coding table selector 2506 selects a coding table to be used for entropyencoding, using the occupancy information of the neighboring nodegenerated by geometry information calculator 2505.

Entropy encoder 2507 generates a bitstream by entropy encoding anoccupancy code of the current node using the selected coding table. Itshould be noted that entropy encoder 2507 may append, to the bitstream,information indicating the selected coding table.

Next, a configuration example of the three-dimensional data decodingdevice according to the present embodiment will be described. FIG. 194is a block diagram of three-dimensional data decoding device 2510according to the present embodiment. Three-dimensional data decodingdevice 2510 includes octree generator 2511, parent node informationobtainer 2512, decoding mode selector 2513, searcher 2514, geometryinformation calculator 2515, coding table selector 2516, and entropydecoder 2517.

Octree generator 2511 generates an octree of a space (nodes) usingheader information etc. of a bitstream. For example, octree generator2511 generates a large space (a root node) using the size of a spacealong the x-axis, y-axis, and z-axis directions appended to the headerinformation, and generates an octree by generating eight small spaces A(nodes A0 to A7) by dividing the space into two along each of thex-axis, y-axis, and z-axis directions. In addition, nodes A0 to A7 areset as a current node in sequence.

Parent node information obtainer 2512 obtains neighboring information ofa neighboring node from an occupancy code of a parent node of a currentnode. In other words, parent node information obtainer 2512 obtains, forexample, neighboring information of neighboring nodes that are, amongneighboring nodes, neighboring nodes belonging to the same parent nodeas the current node and account for half of the neighboring nodes.

Decoding mode selector 2513 selects a decoding mode. For example, thisdecoding mode corresponds to the above encoding mode, and includes amode for performing one of a search process and a process of obtainingneighboring information from an occupancy code of a parent node, and amode for performing the both.

Searcher 2514 obtains neighboring information of a neighboring nodethrough a search process, using information of decoded nodes. Althoughthis search process requires some processing time, the search processmakes it possible to obtain neighboring information of all neighboringnodes.

Geometry information calculator 2515 generates neighboring information(occupancy information of a neighboring node) to be used for selecting acoding table, by using one of the neighboring information obtained byparent node information obtainer 2512 and the neighboring informationobtained by searcher 2514, or by integrating the both.

Coding table selector 2516 selects a coding table to be used for entropydecoding, using the occupancy information of the neighboring nodegenerated by geometry information calculator 2515.

Entropy decoder 2517 generates three-dimensional points (a point cloud)by entropy decoding an occupancy code using the selected coding table.It should be noted that entropy decoder 2517 may obtain information ofthe selected coding table from the bitstream, and entropy decode anoccupancy code of the current node using the coding table indicated bythe information.

Each bit of an occupancy code (8 bits) included in a bitstream indicateswhether a corresponding one of eight small spaces A (node A0 to node A7)includes a point cloud. Moreover, the three-dimensional data decodingdevice generates an octree by dividing small space node A0 into eightsmall spaces B (node B0 to node B7), and calculates informationindicating whether each node of small spaces B includes a point cloud,by decoding an occupancy code. As stated above, the three-dimensionaldata decoding device decodes an occupancy code of each node whilegenerating an octree by dividing a large space into small spaces.

Hereinafter, procedures for a three-dimensional data encoding processand a three-dimensional data decoding process according to the presentembodiment will be described. FIG. 195 is a flowchart of athree-dimensional data encoding process performed by thethree-dimensional data encoding device.

First, the three-dimensional data encoding device defines a space (acurrent node) including part or all of an inputted three-dimensionalpoint cloud (S2501). Next, the three-dimensional data encoding devicegenerates eight small spaces (nodes) by dividing the current node intoeight (S2502). Then, the three-dimensional data encoding devicegenerates an occupancy code of the current node according to whethereach node includes a point cloud (S2503). After that, thethree-dimensional data encoding device calculates neighboringinformation of a neighboring node of the current node from an occupancycode of a parent node of the current node (S2504).

Next, the three-dimensional data encoding device selects an encodingmode (S2505). For example, the three-dimensional data encoding deviceselects an encoding mode for performing a search process. Then, thethree-dimensional data encoding device obtains remaining neighboringinformation by searching for information of encoded nodes. In addition,the three-dimensional data encoding device generates neighboringinformation to be used for selecting a coding table, by integrating theneighboring information calculated in step S2504 and the neighboringinformation obtained by the search process (S2506).

After that, the three-dimensional data encoding device selects a codingtable to be used for entropy encoding, based on the neighboringinformation generated in step S2506 (S2507). Next, the three-dimensionaldata encoding device entropy encodes the occupancy code of the currentnode using the selected coding table (S2508). Finally, thethree-dimensional data encoding device repeats a process of dividingeach node into eight and encoding an occupancy code of each node untileach node cannot be divided (S2509). In other words, steps S2502 toS2508 are recursively repeated;

FIG. 196 is a flowchart of a three-dimensional data decoding processperformed by the three-dimensional data decoding device.

First, the three-dimensional data decoding device defines a space (acurrent node) to be decoded, using header information of a bitstream(S2511). Next, the three-dimensional data decoding device generateseight small spaces (nodes) by dividing the current node into eight(S2512). Then, the three-dimensional data decoding device calculatesneighboring information of a neighboring node of the current node froman occupancy code of a parent node of the current node (S2513).

After that, the three-dimensional data decoding device selects adecoding mode corresponding to the above encoding mode (S2514). Forexample, the three-dimensional data decoding device selects a decodingmode for performing a search process. Next, the three-dimensional datadecoding device obtains remaining neighboring information by searchingfor information of decoded nodes. In addition, the three-dimensionaldata decoding device generates neighboring information to be used forselecting a coding table, by integrating the neighboring informationcalculated in step S2513 and the neighboring information obtained by thesearch process (S2515).

Then, the three-dimensional data decoding device selects a coding tableto be used for entropy decoding, based on the neighboring informationgenerated in step S2515 (S2516). After that, the three-dimensional datadecoding device entropy decodes an occupancy code of the current nodeusing the selected coding table (S2517). Finally, the three-dimensionaldata decoding device repeats a process of dividing each node into eightand decoding an occupancy code of each node until each node cannot bedivided (S2518). In other words, steps S2512 to S2517 are recursivelyrepeated.

The following describes an encoding mode (a decoding mode). An encodingmode includes at least one of (1) the first mode for skipping a searchprocess, (2) the second mode for performing a search process andstopping the process at the above-mentioned search threshold value, or(3) the third mode for performing a search process and searching for allencoded (decoded) nodes.

In other words, the three-dimensional data decoding device may select,as an encoding mode, whether to skip a neighboring node search or tosearch for a neighboring node. Moreover, when the three-dimensional dataencoding device searches for a neighboring node, the three-dimensionaldata encoding device may limit the number of searches to at most apredetermined threshold value. Furthermore, the three-dimensional dataencoding device may append information indicating this threshold valueto the header of a bitstream. Alternatively, the threshold value may bespecified by standards etc. Additionally, the three-dimensional dataencoding device may change the threshold value for each node. Forexample, the number of neighboring node candidates increases as a valueof a layer of an octree increases (deepens). For this reason, thethree-dimensional data encoding device may increase the threshold valueas the value of the layer of the octree increases (deepens). A referablerange may change for each layer to which nodes belong. In other words, arange for one or more referable neighboring nodes among neighboringnodes spatially neighboring a current node may vary according to a layerto which the current node belongs in a tree structure. Here, even whenparameter values indicating a referable range set to a header etc. areidentical, a space represented by a node decreases with a deeper layer.In other words, a range of a space in which nodes are referable may beabsolutely narrower with a deeper layer.

Moreover, the three-dimensional data encoding device may appendinformation indicating an encoding mode to the header of a bitstream. Anencoding mode may be specified by standards etc. In consequence, sincethe three-dimensional data decoding device can determine a decoding mode(an encoding mode) from a decoded header or requirements of standards,the three-dimensional data decoding device can decode a streamcorrectly.

Furthermore, the three-dimensional data encoding device may encode anencoding mode for each node, and change an encoding mode for each node.For example, the three-dimensional data encoding device performsencoding using all encoding modes once, and determines an encoding modemost suitable for the three-dimensional data decoding device from astandpoint of coding efficiency and processing time. Then, thethree-dimensional data encoding device may encode, for each node,information indicating the determined encoding mode. As a result, thethree-dimensional data decoding device can decode a bitstream correctlyby decoding the encoding mode encoded for each node.

Moreover, the three-dimensional data encoding device may encode anencoding mode for each set of predetermined nodes, and change anencoding mode on a set basis. It should be noted that a set of nodes is,for example, a set of nodes included in the same layer of an octree.

It should be noted that the three-dimensional data decoding device mayalso determine a decoding mode (an encoding mode) in the same manner. Inother words, the three-dimensional data encoding device and thethree-dimensional data decoding device may estimate an encoding mode foreach node in the same manner, and select whether to search for aneighboring node for each node. As a result, the three-dimensional dataencoding device and the three-dimensional data decoding device determinewhether a current node requires a neighboring node search, search forthe neighboring node when determining that the current node requires theneighboring node search, and skip the neighboring node search whendetermining that the current node requires no neighboring node search.In addition, it is not necessary to transmit information indicating anencoding mode. Accordingly, it is possible to reduce the amount ofprocessing while improving the coding efficiency.

For example, the three-dimensional data encoding device and thethree-dimensional data decoding device determine whether a current noderequires a neighboring node search, from, for example, an occupancy codeof a parent node. Here, when all of occupancy information of threeneighboring nodes calculated from the occupancy code of the parent nodeare 1, there is a high possibility that other neighboring nodes areoccupied. For this reason, in this case, the three-dimensional dataencoding device and the three-dimensional data decoding device determinethat a current node requires a neighboring node search.

Furthermore, the three-dimensional data encoding device and thethree-dimensional data decoding device may determine whether a currentnode requires a neighboring node search, from a value of a layer of anoctree. For example, when a layer has a small value (is close to a rootnode), there is a high possibility that octree division has not beenperformed sufficiently. For this reason, the three-dimensional dataencoding device and the three-dimensional data decoding device maydetermine that neighboring nodes are likely to be occupied, anddetermine that a current node requires a neighboring node search. Asstated above, the three-dimensional data encoding device and thethree-dimensional data decoding device can perform encoding and decodingcorrectly while reducing the code amount, by estimating an encoding modein the same manner.

Moreover, the three-dimensional data encoding device and thethree-dimensional data decoding device may estimate an encoding mode (adecoding mode) for each set of predetermined nodes in the same manner,and change an encoding mode on a set basis. As a result, thethree-dimensional data encoding device and the three-dimensional datadecoding device determine whether the set of the nodes requires aneighboring node search, search for a neighboring node when determiningthat the set of the nodes requires the neighboring node search, and skipthe neighboring node search when determining that the set of the nodesrequires no neighboring node search. Accordingly, it is possible toreduce the amount of processing while improving the coding efficiency.

It should be noted that a set of nodes is, for example, a set of nodesincluded in the same layer of an octree. Since this enables thethree-dimensional data encoding device and the three-dimensional datadecoding device to select whether to search for a neighboring node foreach layer, the three-dimensional data encoding device and thethree-dimensional data decoding device can improve the coding efficiencywhile reducing the processing time. For example, when a layer has asmall value (is close to a root node), there is a high possibility thatoctree division has not been performed sufficiently. For this reason,the three-dimensional data encoding device and the three-dimensionaldata decoding device may determine that neighboring nodes are likely tobe occupied, and determine that a current node requires a neighboringnode search.

Next, an example of a syntax of information etc. indicating an encodingmode will be described. FIG. 197 is a diagram illustrating an example ofa syntax of header information. FIG. 198 is a diagram illustrating anexample of a syntax of information of a node.

As illustrated in FIG. 197, header information includes coding_mode1 andlimit_num_of_search. coding_mode1 is information indicating whether tosearch for a neighboring node. For example, a value of 0 indicates thata neighboring node is not to be searched for, a value of 1 indicatesthat a neighboring node is to be searched for for all nodes, and a valueof 2 indicates that a neighboring node search is to be changed for eachnode.

It should be noted that the three-dimensional data encoding device mayspecify whether to search for a neighboring node, based on standards ora profile or level etc. of standards, without appending coding_mode1 toa header. This enables the three-dimensional data decoding device todetermine whether the neighboring node has been searched for byreference to standards information, and to restore a bitstreamcorrectly.

limit_num_of_search is information indicating a neighboring thresholdvalue, and indicates, for example, a limit on the number of searches (asearch threshold value) when a neighboring node is searched for. Forexample, a value of 0 indicates no limit on the number of searches, anda value of at least 1 indicates a limit on the number of searches.

limit_num_of_search is included in header information when a value ofcoding_mode1 is at least 1. It should be noted that thethree-dimensional data encoding device need not includelimit_num_of_search in a header when there is always no need to limit asearch. In addition, the three-dimensional data encoding device mayprovide limit_num_of_search for each layer of an octree and includelimit_num_of_search in a header.

Additionally, a value of limit_num_of_search may be determined beforecoding. For example, the value is set to no limit when ahigh-performance device performs encoding or decoding, and the value isset to a limit when a low-performance device performs encoding ordecoding.

As illustrated in FIG. 198, information of a node includes coding_mode2and occupancy_code. coding_mode2 is included in the information of thenode when a value of coding_mode1 is 2. coding_mode2 is informationindicating whether to search for a neighboring node for each node. Forexample, a value of 0 indicates that a neighboring node is not to besearched for, and a value of 1 indicates that a neighboring node is tobe searched for.

It should be noted that when coding_mode2 is 1, the three-dimensionaldata encoding device and the three-dimensional data decoding device mayset a limit on the number of searches to limit_num_of_search appended toa header. Moreover, the three-dimensional data encoding device mayencode, for each node, information indicating a limit on the number ofsearches.

Furthermore, the three-dimensional data encoding device need not encodea value of coding_mode2, and the three-dimensional data decoding devicemay estimate a value of coding_mode2. For example, the three-dimensionaldata decoding device estimates a value of coding_mode2 from an occupancycode of a parent node or layer information of an octree.

occupancy_code is an occupancy code of a current node, and isinformation indicating whether child nodes of the current node areoccupied. The three-dimensional data encoding device and thethree-dimensional data decoding device calculate occupancy informationof a neighboring node according to a value of coding_mode2, and encodeor decode occupancy_code while changing a coding table, based on thevalue.

Moreover, the three-dimensional data encoding device may entropy encodecoding_mode1, limit_num_of_search, or coding_mode2 generated by theabove-mentioned method. For example, the three-dimensional data encodingdevice binarizes each value and performs arithmetic encoding on thevalue.

Although the octree structure has been described as an example in thepresent embodiment, the present disclosure is not necessarily limited tothis. The above-mentioned procedure may be applied to an N-ary tree suchas a binary tree, a quadtree, and a hexadecatree, or other treestructures, where N is an integer greater than or equal to 2.

The following describes the details of a three-dimensional data encodingprocess. FIG. 199 is a flowchart of a three-dimensional data encodingprocess according to the present embodiment. First, thethree-dimensional data encoding device defines a space (a current node)including part or all of an inputted three-dimensional point cloud(S2521). Next, the three-dimensional data encoding device generateseight small spaces (nodes) by dividing the current node into eight(S2522). Then, the three-dimensional data encoding device generates anoccupancy code of the current node according to whether each nodeincludes a point cloud (S2523). After that, the three-dimensional dataencoding device calculates neighboring information of a neighboring nodeof the current node from an occupancy code of a parent node of thecurrent node (S2524).

Next, the three-dimensional data encoding device determines whether toperform a search process, by checking an encoding mode (S2525). Forexample, when (1) coding_mode1 is 1 or (2) coding_mode1 is 2 andcoding_mode2 is 1, the three-dimensional data encoding device determinesto perform a search process (YES in S2525); and in other cases, thethree-dimensional data encoding device performs no search process (NO inS2525). It should be noted that the three-dimensional data encodingdevice determines whether to search for a neighboring node for all nodes(a value of coding_mode1) and whether to search for a neighboring nodefor each node (a value of coding_mode2), by the above-mentioned methodetc.

For example, the three-dimensional data encoding device estimateswhether a current node requires a neighboring node search (a value ofcoding_mode2), from an occupancy code of a parent node. Here, when allof occupancy information of three neighboring nodes calculated from theoccupancy code of the parent node are 1, there is a high possibilitythat the other neighboring nodes are occupied. For this reason, thethree-dimensional data encoding device determines that the current noderequires the neighboring node search (the value of coding_mode2 is 1).In addition, when the three-dimensional data decoding device estimatescoding_mode2, the three-dimensional data encoding device need not encodecoding_mode2.

When the three-dimensional data encoding device performs a searchprocess (YES in S2525), the three-dimensional data encoding deviceobtains remaining neighboring information by searching for informationof encoded nodes. For example, when a value of limit_num_of_search isnot 0 (no limit on the number of searches), the three-dimensional dataencoding device searches for a neighboring node while limiting thenumber of searches according to the value. In addition, thethree-dimensional data encoding device sets a value oflimit_num_of_search using the above-mentioned method etc. Additionally,the three-dimensional data encoding device integrates the neighboringinformation calculated from the occupancy code of the parent node andthe neighboring information obtained by the search process (S2526).Then, the three-dimensional data encoding device selects a coding tableto be used for entropy encoding, based on the neighboring informationgenerated in step S2526 (2527).

In contrast, when the three-dimensional data encoding device performs nosearch process (NO in S2525), the three-dimensional data encoding deviceselects a coding table to be used for entropy encoding, based on theneighboring information calculated from the occupancy code of the parentnode in step S2524 (S2527).

After that, the three-dimensional data encoding device entropy encodesthe occupancy code of the current node using the selected coding table(S2528). Moreover, the three-dimensional data encoding device encodescoding_mode1 and limit_num_of_search as header information. Furthermore,the three-dimensional data encoding device encodes coding_mode2 for eachnode.

Finally, the three-dimensional data encoding device repeats a process ofdividing each node into eight and encoding an occupancy code of eachnode until each node cannot be divided (S2529). In other words, stepsS2522 to S2528 are recursively repeated.

The following describes the details of a three-dimensional data decodingprocess. FIG. 200 is a flowchart of a three-dimensional data decodingprocess according to the present embodiment. First, thethree-dimensional data decoding device defines a space (a current node)to be decoded, using header information of a bitstream (S2531). At thistime, the three-dimensional data decoding device decodes coding_mode1and limit_num_of_search of the header information.

Next, the three-dimensional data decoding device generates eight smallspaces (nodes) by dividing the current node into eight (S2532). Then,the three-dimensional data decoding device calculates neighboringinformation of a neighboring node of the current node from an occupancycode of a parent node of the current node (S2533).

After that, the three-dimensional data decoding device determineswhether to perform a search process, by checking a decoding modecorresponding to an encoding mode (S2534). For example, when (1)coding_mode1 is 1 or (2) coding_mode1 is 2 and coding_mode2 is 1, thethree-dimensional data decoding device determines to perform a searchprocess (YES in S2534); and in other cases, the three-dimensional datadecoding device performs no search process (NO in S2534). In addition,the three-dimensional data decoding device decodes coding_mode2 for, forexample, each node.

It should be noted that the three-dimensional data decoding device maydetermine whether a current node requires a neighboring node search (avalue of coding_mode2), using the same process as the process in thethree-dimensional data encoding device. For example, thethree-dimensional data decoding device estimates whether a current noderequires a neighboring node search, from an occupancy code of a parentnode. Here, when all of occupancy information of three neighboring nodescalculated from the occupancy code of the parent node are 1, there is ahigh possibility that other neighboring nodes are occupied. For thisreason, the three-dimensional data decoding device determines that thecurrent node requires the neighboring node search (the value ofcoding_mode2 is 1). In addition, when the three-dimensional datadecoding device estimates coding_mode2, the three-dimensional datadecoding device need not decode coding_mode2.

Next, when the three-dimensional data decoding device performs a searchprocess (YES in S2534), the three-dimensional data decoding deviceobtains remaining neighboring information by searching for informationof decoded nodes. For example, when a value of limit_num_of_search isnot 0 (no limit on the number of searches), the three-dimensional datadecoding device searches for a neighboring node while limiting thenumber of searches according to the value. Additionally, thethree-dimensional data decoding device integrates the neighboringinformation calculated from the occupancy code of the parent node andthe neighboring information obtained by the search process (S2535).Then, the three-dimensional data decoding device selects a coding tableto be used for entropy decoding, based on the neighboring informationgenerated in step S2535 (S2536).

In contrast, when the three-dimensional data decoding device performs nosearch process (NO in S2534), the three-dimensional data decoding deviceselects a coding table to be used for entropy decoding, based on theneighboring information calculated from the occupancy code of the parentnode in step S2533 and the neighboring information obtained by thesearch process (S2536).

After that, the three-dimensional data decoding device entropy decodesan occupancy code of the current node using the selected coding table(S2537). Finally, the three-dimensional data decoding device repeats aprocess of dividing each node into eight and decoding an occupancy codeof each node until each node cannot be divided (S2538). In other words,steps S2532 to S2537 are recursively repeated.

It should be noted that the above description shows an example in whichnodes to be searched are encoded nodes, nodes to be searched are notnecessarily limited to this. For example, the three-dimensional dataencoding device may obtain information of neighboring nodes of all thenodes belonging to the same layer, by performing a search using themethod described in the present embodiment, and then may encode anoccupancy code of each node using the obtained information of theneighboring nodes.

As stated above, the three-dimensional data encoding device according tothe present embodiment performs the process illustrated in FIG. 201. Thethree-dimensional data encoding device encodes information of a currentnode included in an N-ary tree structure of three-dimensional pointsincluded in three-dimensional data, where N is an integer greater thanor equal to 2. In the encoding, the three-dimensional data encodingdevice encodes first information (e.g., limit_num_of_search) indicatinga range for one or more referable neighboring nodes among neighboringnodes spatially neighboring the current node (S2541), and encodes thecurrent node with reference to a neighboring node within the range(S2542).

With this, since the three-dimensional data encoding device limitsreferable neighboring nodes, the three-dimensional data encoding devicereduces the amount of processing.

For example, in the encoding, the three-dimensional data encoding deviceselects a coding table based on whether the neighboring node within therange includes a three-dimensional point, and entropy encodes theinformation (e.g., an occupancy code) of the current node using thecoding table selected.

For example, in the encoding, the three-dimensional data encoding deviceperforms a search for information of the one or more referableneighboring nodes among the neighboring nodes spatially neighboring thecurrent node, and the first information indicates a range for thesearch.

For example, in the search, the three-dimensional data encoding devicesearches for information of nodes in a predetermined order, and thefirst information indicates a total number of nodes (e.g., a searchthreshold value) on which the search is to be performed.

For example, in the search, indexes of Morton codes are used.

For example, in the encoding, the three-dimensional data encoding deviceencodes second information (coding_mode1) indicating whether the rangefor the one or more referable neighboring nodes is to be limited, andencodes the first information when the second information indicates thatthe range for the one or more referable neighboring nodes is to belimited.

For example, the range for the one or more referable neighboring nodeschanges according to a layer to which the current node belongs in theN-ary tree structure.

For example, the three-dimensional data encoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

Moreover, the three-dimensional data decoding device according to thepresent embodiment performs the process illustrated in FIG. 202. Thethree-dimensional data decoding device decodes information of a currentnode included in an N-ary tree structure of three-dimensional pointsincluded in three-dimensional data, where N is an integer greater thanor equal to 2. In the decoding, the three-dimensional data decodingdevice decodes, from a bitstream, first information (e.g.,limit_num_of_search) indicating a range for one or more referableneighboring nodes among neighboring nodes spatially neighboring thecurrent node (S2551), and decodes the current node with reference to aneighboring node within the range (S2552).

With this, since the three-dimensional data decoding device limitsreferable neighboring nodes, the three-dimensional data decoding devicereduces the amount of processing.

For example, in the decoding, the three-dimensional data decoding deviceselects a coding table based on whether the neighboring node within therange includes a three-dimensional point, and entropy decodes theinformation (e.g., an occupancy code) of the current node using thecoding table selected.

For example, in the decoding, the three-dimensional data decoding deviceperforms a search for information of the one or more referableneighboring nodes among the neighboring nodes spatially neighboring thecurrent node, and the first information indicates a range for thesearch.

For example, in the search, the three-dimensional data decoding devicesearches for information of nodes in a predetermined order, and thefirst information indicates a total number of nodes (e.g., a searchthreshold value) on which the search is to be performed.

For example, in the search, indexes of Morton codes are used.

For example, in the decoding, the three-dimensional data decoding devicedecodes second information (coding_mode1) indicating whether the rangefor the one or more referable neighboring nodes is to be limited, anddecodes the first information when the second information indicates thatthe range for the one or more referable neighboring nodes is to belimited.

For example, the range for the one or more referable neighboring nodeschanges according to a layer to which the current node belongs in theN-ary tree structure.

For example, the three-dimensional data decoding device includes aprocessor and memory, and the processor performs the above process usingthe memory.

A three-dimensional data encoding device, a three-dimensional datadecoding device, and the like according to the embodiments of thepresent disclosure have been described above, but the present disclosureis not limited to these embodiments.

Note that each of the processors included in the three-dimensional dataencoding device, the three-dimensional data decoding device, and thelike according to the above embodiments is typically implemented as alarge-scale integrated (LSI) circuit, which is an integrated circuit(IC). These may take the form of individual chips, or may be partiallyor entirely packaged into a single chip.

Such IC is not limited to an LSI, and thus may be implemented as adedicated circuit or a general-purpose processor. Alternatively, a fieldprogrammable gate array (FPGA) that allows for programming after themanufacture of an LSI, or a reconfigurable processor that allows forreconfiguration of the connection and the setting of circuit cellsinside an LSI may be employed.

Moreover, in the above embodiments, the structural components may beimplemented as dedicated hardware or may be realized by executing asoftware program suited to such structural components. Alternatively,the structural components may be implemented by a program executor suchas a CPU or a processor reading out and executing the software programrecorded in a recording medium such as a hard disk or a semiconductormemory.

The present disclosure may also be implemented as a three-dimensionaldata encoding method, a three-dimensional data decoding method, or thelike executed by the three-dimensional data encoding device, thethree-dimensional data decoding device, and the like.

Also, the divisions of the functional blocks shown in the block diagramsare mere examples, and thus a plurality of functional blocks may beimplemented as a single functional block, or a single functional blockmay be divided into a plurality of functional blocks, or one or morefunctions may be moved to another functional block. Also, the functionsof a plurality of functional blocks having similar functions may beprocessed by single hardware or software in a parallelized ortime-divided manner.

Also, the processing order of executing the steps shown in theflowcharts is a mere illustration for specifically describing thepresent disclosure, and thus may be an order other than the shown order.Also, one or more of the steps may be executed simultaneously (inparallel) with another step.

A three-dimensional data encoding device, a three-dimensional datadecoding device, and the like according to one or more aspects have beendescribed above based on the embodiments, but the present disclosure isnot limited to these embodiments. The one or more aspects may thusinclude forms achieved by making various modifications to the aboveembodiments that can be conceived by those skilled in the art, as wellforms achieved by combining structural components in differentembodiments, without materially departing from the spirit of the presentdisclosure.

Although only some exemplary embodiments of the present disclosure havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of the present disclosure. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to a three-dimensional dataencoding device and a three-dimensional data decoding device.

What is claimed is:
 1. A three-dimensional data encoding method,comprising: encoding information of a current node included in an N-arytree structure of three-dimensional points included in three-dimensionaldata, where N is an integer greater than or equal to 2, wherein in theencoding, first information is encoded, the first information indicatinga range for one or more referable neighboring nodes among neighboringnodes spatially neighboring the current node, and the current node isencoded with reference to a neighboring node within the range.
 2. Thethree-dimensional data encoding method according to claim 1, wherein inthe encoding, a coding table is selected based on whether theneighboring node within the range includes a three-dimensional point,and the information of the current node is entropy encoded using thecoding table selected.
 3. The three-dimensional data encoding methodaccording to claim 1, wherein in the encoding, a search is performed forinformation of the one or more referable neighboring nodes among theneighboring nodes spatially neighboring the current node, and the firstinformation indicates a range for the search.
 4. The three-dimensionaldata encoding method according to claim 3, wherein in the search,information of nodes is searched for in a predetermined order, and thefirst information indicates a total number of nodes on which the searchis to be performed.
 5. The three-dimensional data encoding methodaccording to claim 4, wherein in the search, indexes of Morton codes areused.
 6. The three-dimensional data encoding method according to claim1, wherein in the encoding, second information is encoded, the secondinformation indicating whether the range for the one or more referableneighboring nodes is to be limited, and the first information is encodedwhen the second information indicates that the range for the one or morereferable neighboring nodes is to be limited.
 7. The three-dimensionaldata encoding method according to claim 1, wherein the range for the oneor more referable neighboring nodes changes according to a layer towhich the current node belongs in the N-ary tree structure.
 8. Athree-dimensional data decoding method, comprising: decoding informationof a current node included in an N-ary tree structure ofthree-dimensional points included in three-dimensional data, where N isan integer greater than or equal to 2, wherein in the decoding, firstinformation is decoded from a bitstream, the first informationindicating a range for one or more referable neighboring nodes amongneighboring nodes spatially neighboring the current node, and thecurrent node is decoded with reference to a neighboring node within therange.
 9. The three-dimensional data decoding method according to claim8, wherein in the decoding, a coding table is selected based on whetherthe neighboring node within the range includes a three-dimensionalpoint, and the information of the current node is entropy decoded usingthe coding table selected.
 10. The three-dimensional data decodingmethod according to claim 8, wherein in the decoding, a search isperformed for information of the one or more referable neighboring nodesamong the neighboring nodes spatially neighboring the current node, andthe first information indicates a range for the search.
 11. Thethree-dimensional data decoding method according to claim 10, wherein inthe search, information of nodes is searched for in a predeterminedorder, and the first information indicates a total number of nodes onwhich the search is to be performed.
 12. The three-dimensional datadecoding method according to claim 11, wherein in the search, indexes ofMorton codes are used.
 13. The three-dimensional data decoding methodaccording to claim 8, wherein in the decoding, second information isdecoded, the second information indicating whether the range for the oneor more referable neighboring nodes is to be limited, and the firstinformation is decoded when the second information indicates that therange for the one or more referable neighboring nodes is to be limited.14. The three-dimensional data decoding method according to claim 8,wherein the range for the one or more referable neighboring nodeschanges according to a layer to which the current node belongs in theN-ary tree structure.
 15. A three-dimensional data encoding device,comprising: a processor; and memory, wherein using the memory, theprocessor encodes information of a current node included in an N-arytree structure of three-dimensional points included in three-dimensionaldata, where N is an integer greater than or equal to 2, and wherein inthe encoding, first information is encoded, the first informationindicating a range for one or more referable neighboring nodes amongneighboring nodes spatially neighboring the current node, and thecurrent node is encoded with reference to a neighboring node within therange.
 16. A three-dimensional data decoding device, comprising: aprocessor; and memory, wherein using the memory, the processor decodesinformation of a current node included in an N-ary tree structure ofthree-dimensional points included in three-dimensional data, where N isan integer greater than or equal to 2, and wherein in the decoding,first information is decoded from a bitstream, the first informationindicating a range for one or more referable neighboring nodes amongneighboring nodes spatially neighboring the current node, and thecurrent node is decoded with reference to a neighboring node within therange.